{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-27120", "tracking": { "current_release_date": "2026-03-23T01:03:24.010017Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-27120", "initial_release_date": "2026-02-19T20:39:56.569231Z", "revision_history": [ { "date": "2026-02-19T20:39:56.569231Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-02-19T20:39:59.489725Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-02-20T21:38:36.346245Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (2).| CWES updated (1)." }, { "date": "2026-02-20T21:38:39.398096Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-02-20T22:25:11.487971Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)." }, { "date": "2026-02-20T22:25:15.827396Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-02-21T07:35:01.681765Z", "number": "7", "summary": "NCSC Score updated." }, { "date": "2026-02-21T14:14:49.449248Z", "number": "8", "summary": "Source created.| CVE status created. (valid)| EPSS created." }, { "date": "2026-02-21T14:14:51.488258Z", "number": "9", "summary": "NCSC Score updated." }, { "date": "2026-02-23T03:01:14.179060Z", "number": "10", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (29).| Products created (20).| References created (4).| CWES updated (1)." }, { "date": "2026-02-23T03:01:16.382832Z", "number": "11", "summary": "NCSC Score updated." }, { "date": "2026-02-23T22:39:48.446966Z", "number": "12", "summary": "References created (1)." }, { "date": "2026-02-23T22:39:51.014807Z", "number": "13", "summary": "NCSC Score updated." }, { "date": "2026-02-24T20:02:17.741978Z", "number": "14", "summary": "Unknown change." }, { "date": "2026-02-24T20:02:24.621277Z", "number": "15", "summary": "NCSC Score updated." }, { "date": "2026-03-02T14:25:04.316478Z", "number": "16", "summary": "Products created (1).| Product Identifiers created (1).| Exploits created (1)." }, { "date": "2026-03-02T14:25:06.904582Z", "number": "17", "summary": "NCSC Score updated." }, { "date": "2026-03-20T09:42:32.055797Z", "number": "18", "summary": "Source connected.| CVE status created. (valid)| EPSS created." } ], "status": "interim", "version": "18" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<1.14.1", "product": { "name": "vers:unknown/<1.14.1", "product_id": "CSAFPID-5753416", "product_identification_helper": { "cpe": "cpe:2.3:a:vapor:leafkit:*:*:*:*:*:*:*:*" } } } ], "category": "product_name", "name": "LeafKit" }, { "branches": [ { "category": "product_version_range", "name": "vers:unknown/1.0.0", "product": { "name": "vers:unknown/1.0.0", "product_id": "CSAFPID-4336745" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-alpha.1", "product": { "name": "vers:unknown/1.0.0-alpha.1", "product_id": "CSAFPID-4336746" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-beta.2", "product": { "name": "vers:unknown/1.0.0-beta.2", "product_id": "CSAFPID-4336747" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-beta.2.1", "product": { "name": "vers:unknown/1.0.0-beta.2.1", "product_id": "CSAFPID-4336748" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-beta.2.2", "product": { "name": "vers:unknown/1.0.0-beta.2.2", "product_id": "CSAFPID-4336749" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1", "product": { "name": "vers:unknown/1.0.0-rc.1", "product_id": "CSAFPID-4336750" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.1", "product": { "name": "vers:unknown/1.0.0-rc.1.1", "product_id": "CSAFPID-4336751" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.10", "product": { "name": "vers:unknown/1.0.0-rc.1.10", "product_id": "CSAFPID-4336752" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.11", "product": { "name": "vers:unknown/1.0.0-rc.1.11", "product_id": "CSAFPID-4336753" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.12", "product": { "name": "vers:unknown/1.0.0-rc.1.12", "product_id": "CSAFPID-4336754" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.13", "product": { "name": "vers:unknown/1.0.0-rc.1.13", "product_id": "CSAFPID-4336755" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.14", "product": { "name": "vers:unknown/1.0.0-rc.1.14", "product_id": "CSAFPID-4336756" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.15", "product": { "name": "vers:unknown/1.0.0-rc.1.15", "product_id": "CSAFPID-4336757" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.16", "product": { "name": "vers:unknown/1.0.0-rc.1.16", "product_id": "CSAFPID-4336758" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.17", "product": { "name": "vers:unknown/1.0.0-rc.1.17", "product_id": "CSAFPID-4336759" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.2", "product": { "name": "vers:unknown/1.0.0-rc.1.2", "product_id": "CSAFPID-4336760" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.3", "product": { "name": "vers:unknown/1.0.0-rc.1.3", "product_id": "CSAFPID-4336761" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.4", "product": { "name": "vers:unknown/1.0.0-rc.1.4", "product_id": "CSAFPID-4336762" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.5", "product": { "name": "vers:unknown/1.0.0-rc.1.5", "product_id": "CSAFPID-4336763" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.6", "product": { "name": "vers:unknown/1.0.0-rc.1.6", "product_id": "CSAFPID-4336764" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.7", "product": { "name": "vers:unknown/1.0.0-rc.1.7", "product_id": "CSAFPID-4336765" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.8", "product": { "name": "vers:unknown/1.0.0-rc.1.8", "product_id": "CSAFPID-4336766" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-rc.1.9", "product": { "name": "vers:unknown/1.0.0-rc.1.9", "product_id": "CSAFPID-4336767" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-tau.1", "product": { "name": "vers:unknown/1.0.0-tau.1", "product_id": "CSAFPID-4336768" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-tau.1.1", "product": { "name": "vers:unknown/1.0.0-tau.1.1", "product_id": "CSAFPID-4336769" } }, { "category": "product_version_range", "name": "vers:unknown/1.0.0-zeta.1", "product": { "name": "vers:unknown/1.0.0-zeta.1", "product_id": "CSAFPID-4336770" } }, { "category": "product_version_range", "name": "vers:unknown/1.1.0", "product": { "name": "vers:unknown/1.1.0", "product_id": "CSAFPID-4336771" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.0", "product": { "name": "vers:unknown/1.10.0", "product_id": "CSAFPID-5668209" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.1", "product": { "name": "vers:unknown/1.10.1", "product_id": "CSAFPID-5668210" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.2", "product": { "name": "vers:unknown/1.10.2", "product_id": "CSAFPID-5668211" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.3", "product": { "name": "vers:unknown/1.10.3", "product_id": "CSAFPID-5668212" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.4", "product": { "name": "vers:unknown/1.10.4", "product_id": "CSAFPID-5668213" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.5", "product": { "name": "vers:unknown/1.10.5", "product_id": "CSAFPID-5668214" } }, { "category": "product_version_range", "name": "vers:unknown/1.10.6", "product": { "name": "vers:unknown/1.10.6", "product_id": "CSAFPID-5668215" } }, { "category": "product_version_range", "name": "vers:unknown/1.11.0", "product": { "name": "vers:unknown/1.11.0", "product_id": "CSAFPID-5668216" } }, { "category": "product_version_range", "name": "vers:unknown/1.11.1", "product": { "name": "vers:unknown/1.11.1", "product_id": "CSAFPID-5668217" } }, { "category": "product_version_range", "name": "vers:unknown/1.12.0", "product": { "name": "vers:unknown/1.12.0", "product_id": "CSAFPID-5668218" } }, { "category": "product_version_range", "name": "vers:unknown/1.13.0", "product": { "name": "vers:unknown/1.13.0", "product_id": "CSAFPID-5668219" } }, { "category": "product_version_range", "name": "vers:unknown/1.13.1", "product": { "name": "vers:unknown/1.13.1", "product_id": "CSAFPID-5668220" } }, { "category": "product_version_range", "name": "vers:unknown/1.14.0", "product": { "name": "vers:unknown/1.14.0", "product_id": "CSAFPID-5668221" } }, { "category": "product_version_range", "name": "vers:unknown/1.2.0", "product": { "name": "vers:unknown/1.2.0", "product_id": "CSAFPID-4336772" } }, { "category": "product_version_range", "name": "vers:unknown/1.3.0", "product": { "name": "vers:unknown/1.3.0", "product_id": "CSAFPID-5668222" } }, { "category": "product_version_range", "name": "vers:unknown/1.3.1", "product": { "name": "vers:unknown/1.3.1", "product_id": "CSAFPID-5668223" } }, { "category": "product_version_range", "name": "vers:unknown/1.4.0", "product": { "name": "vers:unknown/1.4.0", "product_id": "CSAFPID-5657636" } }, { "category": "product_version_range", "name": "vers:unknown/1.5.0", "product": { "name": "vers:unknown/1.5.0", "product_id": "CSAFPID-5668224" } }, { "category": "product_version_range", "name": "vers:unknown/1.6.0", "product": { "name": "vers:unknown/1.6.0", "product_id": "CSAFPID-5668225" } }, { "category": "product_version_range", "name": "vers:unknown/1.7.0", "product": { "name": "vers:unknown/1.7.0", "product_id": "CSAFPID-5668226" } }, { "category": "product_version_range", "name": "vers:unknown/1.8.0", "product": { "name": "vers:unknown/1.8.0", "product_id": "CSAFPID-5668227" } }, { "category": "product_version_range", "name": "vers:unknown/1.9.0", "product": { "name": "vers:unknown/1.9.0", "product_id": "CSAFPID-5668228" } }, { "category": "product_version_range", "name": "vers:unknown/<1.4.1", "product": { "name": "vers:unknown/<1.4.1", "product_id": "CSAFPID-5653680" } } ], "category": "product_name", "name": "leaf-kit" } ], "category": "vendor", "name": "Vapor" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-27120", "cwe": { "id": "CWE-79", "name": "Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')" }, "notes": [ { "category": "description", "text": "### Summary\n\n`htmlEscaped` in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled.\n\n### Details\n\nRelevant code:\nhttps://github.com/vapor/leaf-kit/blob/main/Sources/LeafKit/String%2BHTMLEscape.swift#L14\n\nStrings in Swift are based on extended grapheme clusters. HTML on the other hand is based on unicode characters. \n\nFor example if you have the sequence \"́ (U+0022 Quotation mark followed by U+0301 Combining Acute Accent). To HTML this is just a quote mark followed by some other random character. To swift this is one extended grapheme cluster that does not equal a quotation mark by itself which is a different extended grapheme cluster.\n\nThus `\"\\\"́\".replacingOccurrences(of: \"\\\"\", with: \""\")` does not replace the quote mark. This allows you to break out of html attributes.\n\nI believe replacingOccurences takes an optional third parameter that allows you to specify options to make it work on UTF-8 characters instead of grapheme clusters, which would be a good fix for this issue.\n\nI see depending on version, leafkit might use `replacing` instead of `replacingOccurences`. I don't know swift that well and couldn't find docs on what replacing does, so I don't know if both versions of the function are affected. The version of swift i was testing on I believe was using replacingOccurences\n\nIt seems like replacingOccurences will skip past prefix characters of extended grapheme clusters, which is what would be needed in order to meaningfully bypass esaping of <. Thus i think this is mostly limited to attributes and not general text.\n\n### PoC\n\nAn example vapor application that is vulnerable might look like\n\nroutes.swift\n```swift\nimport Vapor\n\nstruct Hello: Content {\n var msg: String?\n}\n\nfunc routes(_ app: Application) throws {\n app.post { req throws in\n\tlet Hello = try req.content.decode(Hello.self)\n return req.view.render(\"hello\", [\n \"msg\": Hello.msg ?? \"Hello World!\"\n ])\n }\n}\n```\n\nWith a hello.leaf that looks like\n```\n
Hover to see message
\n```\n\nAnd then you POST something like `msg=%22%cc%81=1%20autofocus%20tabindex=0%20onfocus=alert(1)%20`\n\n### Impact\nIf a website uses leaf to escape an attribute value based on user input, the attacker may be able to insert a malicious attribute. If a site is not using a secure CSP policy, then this can be used to execute malicious javascript (XSS). Impact is context dependent if a site is using a secure CSP policy.", "title": "github - https://github.com/advisories/GHSA-4hfh-fch3-5q7p" }, { "category": "description", "text": "Leafkit is a templating language with Swift-inspired syntax. Prior to 1.4.1, htmlEscaped in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled. This vulnerability is fixed in 1.4.1.", "title": "cveprojectv5 - https://www.cve.org/CVERecord?id=CVE-2026-27120" }, { "category": "description", "text": "Leafkit is a templating language with Swift-inspired syntax. Prior to 1.4.1, htmlEscaped in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled. This vulnerability is fixed in 1.4.1.", "title": "nvd - https://nvd.nist.gov/vuln/detail/CVE-2026-27120" }, { "category": "description", "text": "Leafkit is a templating language with Swift-inspired syntax. Prior to 1.4.1, htmlEscaped in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled. This vulnerability is fixed in 1.4.1.", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-27120.json?alt=media" }, { "category": "other", "text": "0.00031", "title": "EPSS" }, { "category": "other", "text": "4.4", "title": "NCSC Score" }, { "category": "other", "text": "Is related to an uncommon cwe id", "title": "NCSC Score top increasing factors" }, { "category": "other", "text": "There is exploit data available from source Nvd", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5653680", "CSAFPID-4336745", "CSAFPID-4336746", "CSAFPID-4336747", "CSAFPID-4336748", "CSAFPID-4336749", "CSAFPID-4336750", "CSAFPID-4336751", "CSAFPID-4336752", "CSAFPID-4336753", "CSAFPID-4336754", "CSAFPID-4336755", "CSAFPID-4336756", "CSAFPID-4336757", "CSAFPID-4336758", "CSAFPID-4336759", "CSAFPID-4336760", "CSAFPID-4336761", "CSAFPID-4336762", "CSAFPID-4336763", "CSAFPID-4336764", "CSAFPID-4336765", "CSAFPID-4336766", "CSAFPID-4336767", "CSAFPID-4336768", "CSAFPID-4336769", "CSAFPID-4336770", "CSAFPID-4336771", "CSAFPID-4336772", "CSAFPID-5657636", "CSAFPID-5668209", "CSAFPID-5668210", "CSAFPID-5668211", "CSAFPID-5668212", "CSAFPID-5668213", "CSAFPID-5668214", "CSAFPID-5668215", "CSAFPID-5668216", "CSAFPID-5668217", "CSAFPID-5668218", "CSAFPID-5668219", "CSAFPID-5668220", "CSAFPID-5668221", "CSAFPID-5668222", "CSAFPID-5668223", "CSAFPID-5668224", "CSAFPID-5668225", "CSAFPID-5668226", "CSAFPID-5668227", "CSAFPID-5668228", "CSAFPID-5753416" ] }, "references": [ { "category": "external", "summary": "Source - github", "url": "https://github.com/advisories/GHSA-4hfh-fch3-5q7p" }, { "category": "external", "summary": "Source raw - github", "url": "https://api.github.com/advisories/GHSA-4hfh-fch3-5q7p" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://www.cve.org/CVERecord?id=CVE-2026-27120" }, { "category": "external", "summary": "Source raw - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/27xxx/CVE-2026-27120.json" }, { "category": "external", "summary": "Source - nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27120" }, { "category": "external", "summary": "Source raw - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-27120" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-27120" }, { "category": "external", "summary": "Source raw - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-27120.json?alt=media" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd; osv", "url": "https://github.com/vapor/leaf-kit/security/advisories/GHSA-4hfh-fch3-5q7p" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd; osv", "url": "https://github.com/vapor/leaf-kit/commit/8919e39476c3a4ba05c28b71546bb9195f87ef34" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-4hfh-fch3-5q7p" }, { "category": "external", "summary": "Reference - osv", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27120.json" }, { "category": "external", "summary": "Reference - github; osv", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27120" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM" }, "products": [ "CSAFPID-4336745", "CSAFPID-4336746", "CSAFPID-4336747", "CSAFPID-4336748", "CSAFPID-4336749", "CSAFPID-4336750", "CSAFPID-4336751", "CSAFPID-4336752", "CSAFPID-4336753", "CSAFPID-4336754", "CSAFPID-4336755", "CSAFPID-4336756", "CSAFPID-4336757", "CSAFPID-4336758", "CSAFPID-4336759", "CSAFPID-4336760", "CSAFPID-4336761", "CSAFPID-4336762", "CSAFPID-4336763", "CSAFPID-4336764", "CSAFPID-4336765", "CSAFPID-4336766", "CSAFPID-4336767", "CSAFPID-4336768", "CSAFPID-4336769", "CSAFPID-4336770", "CSAFPID-4336771", "CSAFPID-4336772", "CSAFPID-5653680", "CSAFPID-5657636", "CSAFPID-5668209", "CSAFPID-5668210", "CSAFPID-5668211", "CSAFPID-5668212", "CSAFPID-5668213", "CSAFPID-5668214", "CSAFPID-5668215", "CSAFPID-5668216", "CSAFPID-5668217", "CSAFPID-5668218", "CSAFPID-5668219", "CSAFPID-5668220", "CSAFPID-5668221", "CSAFPID-5668222", "CSAFPID-5668223", "CSAFPID-5668224", "CSAFPID-5668225", "CSAFPID-5668226", "CSAFPID-5668227", "CSAFPID-5668228", "CSAFPID-5753416" ] } ], "title": "CVE-2026-27120" } ] }