{ "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-2026-27017", "tracking": { "current_release_date": "2026-03-22T17:52:29.895339Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-27017", "initial_release_date": "2026-02-18T22:39:47.943648Z", "revision_history": [ { "date": "2026-02-18T22:39:47.943648Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)." }, { "date": "2026-02-18T22:39:51.420947Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-02-20T03:24:59.776604Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)." }, { "date": "2026-02-20T03:25:05.755686Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-02-20T03:39:46.073999Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (1).| CWES updated (1)." }, { "date": "2026-02-20T03:39:56.854408Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-02-20T14:13:26.886955Z", "number": "7", "summary": "Source created.| CVE status created. (valid)| EPSS created." }, { "date": "2026-02-20T14:13:29.180001Z", "number": "8", "summary": "NCSC Score updated." }, { "date": "2026-02-20T15:50:39.550726Z", "number": "9", "summary": "Unknown change." }, { "date": "2026-02-20T15:50:46.383761Z", "number": "10", "summary": "NCSC Score updated." }, { "date": "2026-02-20T17:39:40.955671Z", "number": "11", "summary": "References created (1)." }, { "date": "2026-02-20T19:29:13.115512Z", "number": "12", "summary": "CVSS created.| Products connected (1).| Product Identifiers created (1)." }, { "date": "2026-02-20T19:29:18.540227Z", "number": "13", "summary": "NCSC Score updated." }, { "date": "2026-02-21T00:28:55.638183Z", "number": "14", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (13).| References created (3).| CWES updated (1)." }, { "date": "2026-02-21T00:29:04.801555Z", "number": "15", "summary": "NCSC Score updated." }, { "date": "2026-02-23T00:12:32.138243Z", "number": "16", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (1).| References created (4).| CWES updated (1)." }, { "date": "2026-02-23T00:42:55.624367Z", "number": "17", "summary": "Source created.| CVE status created. (valid)| Description created for source.| Products created (2)." }, { "date": "2026-02-25T00:12:41.612963Z", "number": "18", "summary": "Source created.| CVE status created. (valid)| Description created for source.| References created (3)." }, { "date": "2026-02-27T20:39:37.039738Z", "number": "19", "summary": "References created (1)." }, { "date": "2026-02-28T12:12:53.919597Z", "number": "20", "summary": "References created (1)." }, { "date": "2026-03-20T09:42:47.822246Z", "number": "21", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-03-20T19:14:30.746694Z", "number": "22", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (2).| References created (7).| CWES updated (1)." }, { "date": "2026-03-20T19:14:32.755365Z", "number": "23", "summary": "NCSC Score updated." } ], "status": "interim", "version": "23" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/1.8.1", "product": { "name": "vers:unknown/1.8.1", "product_id": "CSAFPID-5875606" } }, { "category": "product_version_range", "name": "vers:unknown/>=1.6.0|<1.8.1", "product": { "name": "vers:unknown/>=1.6.0|<1.8.1", "product_id": "CSAFPID-5875607" } } ], "category": "product_name", "name": "go/github.com/refraction-networking/utls" }, { "branches": [ { "category": "product_version_range", "name": "vers:unknown/>=1.6.0|<1.8.1", "product": { "name": "vers:unknown/>=1.6.0|<1.8.1", "product_id": "CSAFPID-5643603", "product_identification_helper": { "cpe": "cpe:2.3:a:refraction-networking:utls:*:*:*:*:*:go:*:*" } } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.0", "product": { "name": "vers:unknown/v1.6.0", "product_id": "CSAFPID-5656109" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.1", "product": { "name": "vers:unknown/v1.6.1", "product_id": "CSAFPID-5656110" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.2", "product": { "name": "vers:unknown/v1.6.2", "product_id": "CSAFPID-5656111" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.3", "product": { "name": "vers:unknown/v1.6.3", "product_id": "CSAFPID-5656112" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.4", "product": { "name": "vers:unknown/v1.6.4", "product_id": "CSAFPID-5656113" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.5", "product": { "name": "vers:unknown/v1.6.5", "product_id": "CSAFPID-5656114" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.6", "product": { "name": "vers:unknown/v1.6.6", "product_id": "CSAFPID-5656115" } }, { "category": "product_version_range", "name": "vers:unknown/v1.6.7", "product": { "name": "vers:unknown/v1.6.7", "product_id": "CSAFPID-5656116" } }, { "category": "product_version_range", "name": "vers:unknown/v1.7.0", "product": { "name": "vers:unknown/v1.7.0", "product_id": "CSAFPID-5656117" } }, { "category": "product_version_range", "name": "vers:unknown/v1.7.1", "product": { "name": "vers:unknown/v1.7.1", "product_id": "CSAFPID-5656118" } }, { "category": "product_version_range", "name": "vers:unknown/v1.7.2", "product": { "name": "vers:unknown/v1.7.2", "product_id": "CSAFPID-5656119" } }, { "category": "product_version_range", "name": "vers:unknown/v1.7.3", "product": { "name": "vers:unknown/v1.7.3", "product_id": "CSAFPID-5656120" } }, { "category": "product_version_range", "name": "vers:unknown/v1.8.0", "product": { "name": "vers:unknown/v1.8.0", "product_id": "CSAFPID-5656121" } } ], "category": "product_name", "name": "utls" } ], "category": "vendor", "name": "refraction-networking" }, { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/*", "product": { "name": "vers:deb/*", "product_id": "CSAFPID-5667941" } } ], "category": "product_name", "name": "golang-refraction-networking-utls" } ], "category": "product_family", "name": "bookworm" }, { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/*", "product": { "name": "vers:deb/*", "product_id": "CSAFPID-5667942" } } ], "category": "product_name", "name": "golang-refraction-networking-utls" } ], "category": "product_family", "name": "bullseye" } ], "category": "vendor", "name": "debian" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-27017", "cwe": { "id": "CWE-1240", "name": "Use of a Cryptographic Primitive with a Risky Implementation" }, "notes": [ { "category": "description", "text": "There is a fingerprint mismatch with Chrome when using GREASE ECH, having to do with ciphersuite selection. When Chrome selects the preferred ciphersuite in the outer ClientHello and the ciphersuite for ECH, it does so consistently based on hardware support. That means, for example, if it prefers AES for the outer ciphersuite, it would also use AES for ECH. The Chrome parrot in utls hardcodes AES preference for outer ciphersuites but selects the ECH ciphersuite randomly between AES and ChaCha20. So there is a 50% chance of selecting ChaCha20 for ECH while using AES for the outer ciphersuite, which is impossible in Chrome.\n\nThis is only a problem in GREASE ECH, since in real ECH Chrome selects the first valid ciphersuite when AES is preferred, which is the same in utls. So no change is done there.\n\nAffected symbols: `HelloChrome_120`, `HelloChrome_120_PQ`, `HelloChrome_131`, `HelloChrome_133`\n\nFix commit: 24bd1e05a788c1add7f3037f4532ea552b2cee07\n\nThanks to telegram @acgdaily for reporting this issue.", "title": "github - https://github.com/advisories/GHSA-7m29-f4hw-g2vx" }, { "category": "description", "text": "uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. Versions 1.6.0 through 1.8.0 contain a fingerprint mismatch with Chrome when using GREASE ECH, related to cipher suite selection. When Chrome selects the preferred cipher suite in the outer ClientHello and for ECH, it does so consistently based on hardware support—for example, if it prefers AES for the outer cipher suite, it also uses AES for ECH. However, the Chrome parrot in uTLS hardcodes AES preference for outer cipher suites but selects the ECH cipher suite randomly between AES and ChaCha20. This creates a 50% chance of selecting ChaCha20 for ECH while using AES for the outer cipher suite, a combination impossible in Chrome. This issue only affects GREASE ECH; in real ECH, Chrome selects the first valid cipher suite when AES is preferred, which uTLS handles correctly. This issue has been fixed in version 1.8.1.", "title": "nvd - https://nvd.nist.gov/vuln/detail/CVE-2026-27017" }, { "category": "description", "text": "uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. Versions 1.6.0 through 1.8.0 contain a fingerprint mismatch with Chrome when using GREASE ECH, related to cipher suite selection. When Chrome selects the preferred cipher suite in the outer ClientHello and for ECH, it does so consistently based on hardware support—for example, if it prefers AES for the outer cipher suite, it also uses AES for ECH. However, the Chrome parrot in uTLS hardcodes AES preference for outer cipher suites but selects the ECH cipher suite randomly between AES and ChaCha20. This creates a 50% chance of selecting ChaCha20 for ECH while using AES for the outer cipher suite, a combination impossible in Chrome. This issue only affects GREASE ECH; in real ECH, Chrome selects the first valid cipher suite when AES is preferred, which uTLS handles correctly. This issue has been fixed in version 1.8.1.", "title": "cveprojectv5 - https://www.cve.org/CVERecord?id=CVE-2026-27017" }, { "category": "description", "text": "uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. Versions 1.6.0 through 1.8.0 contain a fingerprint mismatch with Chrome when using GREASE ECH, related to cipher suite selection. When Chrome selects the preferred cipher suite in the outer ClientHello and for ECH, it does so consistently based on hardware support—for example, if it prefers AES for the outer cipher suite, it also uses AES for ECH. However, the Chrome parrot in uTLS hardcodes AES preference for outer cipher suites but selects the ECH cipher suite randomly between AES and ChaCha20. This creates a 50% chance of selecting ChaCha20 for ECH while using AES for the outer cipher suite, a combination impossible in Chrome. This issue only affects GREASE ECH; in real ECH, Chrome selects the first valid cipher suite when AES is preferred, which uTLS handles correctly. This issue has been fixed in version 1.8.1.", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-27017.json?alt=media" }, { "category": "description", "text": "There is a fingerprint mismatch with Chrome when using GREASE ECH, having to do with ciphersuite selection. When Chrome selects the preferred ciphersuite in the outer ClientHello and the ciphersuite for ECH, it does so consistently based on hardware support. That means, for example, if it prefers AES for the outer ciphersuite, it would also use AES for ECH. The Chrome parrot in utls hardcodes AES preference for outer ciphersuites but selects the ECH ciphersuite randomly between AES and ChaCha20. So there is a 50% chance of selecting ChaCha20 for ECH while using AES for the outer ciphersuite, which is impossible in Chrome.\n\nThis is only a problem in GREASE ECH, since in real ECH Chrome selects the first valid ciphersuite when AES is preferred, which is the same in utls. So no change is done there.\n\nAffected symbols: `HelloChrome_120`, `HelloChrome_120_PQ`, `HelloChrome_131`, `HelloChrome_133`\n\nFix commit: 24bd1e05a788c1add7f3037f4532ea552b2cee07\n\nThanks to telegram @acgdaily for reporting this issue.", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGHSA-7m29-f4hw-g2vx.json?alt=media" }, { "category": "description", "text": "uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. Versions 1.6.0 through 1.8.0 contain a fingerprint mismatch with Chrome when using GREASE ECH, related to cipher suite selection. When Chrome selects the preferred cipher suite in the outer ClientHello and for ECH, it does so consistently based on hardware support—for example, if it prefers AES for the outer cipher suite, it also uses AES for ECH. However, the Chrome parrot in uTLS hardcodes AES preference for outer cipher suites but selects the ECH cipher suite randomly between AES and ChaCha20. This creates a 50% chance of selecting ChaCha20 for ECH while using AES for the outer cipher suite, a combination impossible in Chrome. This issue only affects GREASE ECH; in real ECH, Chrome selects the first valid cipher suite when AES is preferred, which uTLS handles correctly. This issue has been fixed in version 1.8.1.", "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-27017" }, { "category": "description", "text": "Fingerprint vulnerability in uTLS from GREASE ECH mismatch for Chrome parrots in github.com/refraction-networking/utls", "title": "osv - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGO-2026-4509.json?alt=media" }, { "category": "description", "text": "There is a fingerprint mismatch with Chrome when using GREASE ECH, having to do with ciphersuite selection. When Chrome selects the preferred ciphersuite in the outer ClientHello and the ciphersuite for ECH, it does so consistently based on hardware support. That means, for example, if it prefers AES for the outer ciphersuite, it would also use AES for ECH. The Chrome parrot in utls hardcodes AES preference for outer ciphersuites but selects the ECH ciphersuite randomly between AES and ChaCha20. So there is a 50% chance of selecting ChaCha20 for ECH while using AES for the outer ciphersuite, which is impossible in Chrome.\n\nThis is only a problem in GREASE ECH, since in real ECH Chrome selects the first valid ciphersuite when AES is preferred, which is the same in utls. So no change is done there.\n\nAffected symbols: `HelloChrome_120`, `HelloChrome_120_PQ`, `HelloChrome_131`, `HelloChrome_133`\n\nFix commit: 24bd1e05a788c1add7f3037f4532ea552b2cee07\n\nThanks to telegram @acgdaily for reporting this issue.", "title": "gitlab - https://gitlab.com/api/v4/projects/25847700/repository/files/go%2Fgithub.com%2Frefraction-networking%2Futls%2FCVE-2026-27017.yml/raw" }, { "category": "other", "text": "0.00016", "title": "EPSS" }, { "category": "other", "text": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N", "title": "CVSSV4" }, { "category": "other", "text": "2.3", "title": "CVSSV4 base score" }, { "category": "other", "text": "4.4", "title": "NCSC Score" }, { "category": "other", "text": "The value of the most recent EPSS score, There is cwe data available from source Nvd", "title": "NCSC Score top decreasing factors" } ], "product_status": { "fixed": [ "CSAFPID-5875606" ], "known_affected": [ "CSAFPID-5643603", "CSAFPID-5656109", "CSAFPID-5656110", "CSAFPID-5656111", "CSAFPID-5656112", "CSAFPID-5656113", "CSAFPID-5656114", "CSAFPID-5656115", "CSAFPID-5656116", "CSAFPID-5656117", "CSAFPID-5656118", "CSAFPID-5656119", "CSAFPID-5656120", "CSAFPID-5656121", "CSAFPID-5875607" ], "known_not_affected": [ "CSAFPID-5667941", "CSAFPID-5667942" ] }, "references": [ { "category": "external", "summary": "Source - github", "url": "https://github.com/advisories/GHSA-7m29-f4hw-g2vx" }, { "category": "external", "summary": "Source raw - github", "url": "https://api.github.com/advisories/GHSA-7m29-f4hw-g2vx" }, { "category": "external", "summary": "Source - nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27017" }, { "category": "external", "summary": "Source raw - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-27017" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://www.cve.org/CVERecord?id=CVE-2026-27017" }, { "category": "external", "summary": "Source raw - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/27xxx/CVE-2026-27017.json" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-27017" }, { "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-2026-27017.json?alt=media" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGHSA-7m29-f4hw-g2vx.json?alt=media" }, { "category": "external", "summary": "Source - debian", "url": "https://security-tracker.debian.org/tracker/CVE-2026-27017" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/Go%2FGO-2026-4509.json?alt=media" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Source - gitlab", "url": "https://gitlab.com/api/v4/projects/25847700/repository/files/go%2Fgithub.com%2Frefraction-networking%2Futls%2FCVE-2026-27017.yml/raw" }, { "category": "external", "summary": "Reference - cveprojectv5; github; gitlab; nvd; osv", "url": "https://github.com/refraction-networking/utls/security/advisories/GHSA-7m29-f4hw-g2vx" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://github.com/refraction-networking/utls/commit/24bd1e05a788c1add7f3037f4532ea552b2cee07" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://github.com/refraction-networking/utls/releases/tag/v1.8.1" }, { "category": "external", "summary": "Reference - github; gitlab", "url": "https://github.com/advisories/GHSA-7m29-f4hw-g2vx" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27017" }, { "category": "external", "summary": "Reference - osv", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27017.json" }, { "category": "external", "summary": "Reference - github; gitlab; osv", "url": "https://pkg.go.dev/vuln/GO-2026-4509" }, { "category": "external", "summary": "Reference - gitlab", "url": "https://github.com/refraction-networking/utls" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM" }, "products": [ "CSAFPID-5643603", "CSAFPID-5656109", "CSAFPID-5656110", "CSAFPID-5656111", "CSAFPID-5656112", "CSAFPID-5656113", "CSAFPID-5656114", "CSAFPID-5656115", "CSAFPID-5656116", "CSAFPID-5656117", "CSAFPID-5656118", "CSAFPID-5656119", "CSAFPID-5656120", "CSAFPID-5656121", "CSAFPID-5875607" ] } ], "title": "CVE-2026-27017" } ] }