{
"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-2026-33027",
"tracking": {
"current_release_date": "2026-04-01T23:20:37.997824Z",
"generator": {
"date": "2026-02-17T15:00:00Z",
"engine": {
"name": "V.E.L.M.A",
"version": "1.7"
}
},
"id": "CVE-2026-33027",
"initial_release_date": "2026-03-30T16:52:58.321001Z",
"revision_history": [
{
"date": "2026-03-30T16:52:58.321001Z",
"number": "1",
"summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)."
},
{
"date": "2026-03-30T16:53:06.602162Z",
"number": "2",
"summary": "NCSC Score created."
},
{
"date": "2026-03-30T18:26:19.466082Z",
"number": "3",
"summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)."
},
{
"date": "2026-03-30T18:26:21.316506Z",
"number": "4",
"summary": "NCSC Score updated."
},
{
"date": "2026-03-30T18:39:40.042410Z",
"number": "5",
"summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (2).| CWES updated (1)."
},
{
"date": "2026-03-30T18:39:41.583407Z",
"number": "6",
"summary": "NCSC Score updated."
},
{
"date": "2026-03-30T19:39:06.410488Z",
"number": "7",
"summary": "Unknown change."
},
{
"date": "2026-03-30T22:12:53.421901Z",
"number": "8",
"summary": "References created (1)."
},
{
"date": "2026-03-31T12:05:47.112071Z",
"number": "9",
"summary": "Source connected.| CVE status created. (valid)| Products connected (1).| References created (15)."
},
{
"date": "2026-03-31T12:05:53.584296Z",
"number": "10",
"summary": "NCSC Score updated."
},
{
"date": "2026-03-31T16:58:07.342722Z",
"number": "11",
"summary": "Source connected.| CVE status created. (valid)| EPSS created."
},
{
"date": "2026-03-31T16:58:09.278671Z",
"number": "12",
"summary": "NCSC Score updated."
},
{
"date": "2026-04-01T22:58:42.062924Z",
"number": "13",
"summary": "CVSS created.| Products created (1).| Product Identifiers created (1).| Exploits created (1)."
},
{
"date": "2026-04-01T22:58:44.907351Z",
"number": "14",
"summary": "NCSC Score updated."
}
],
"status": "interim",
"version": "14"
}
},
"product_tree": {
"branches": [
{
"branches": [
{
"branches": [
{
"category": "product_version_range",
"name": "vers:unknown/ui <2.3.4",
"product": {
"name": "vers:unknown/ui <2.3.4",
"product_id": "CSAFPID-5968318"
}
}
],
"category": "product_name",
"name": "NGINX"
}
],
"category": "vendor",
"name": "NGINX"
},
{
"branches": [
{
"branches": [
{
"category": "product_version_range",
"name": "vers:unknown/<2.3.4",
"product": {
"name": "vers:unknown/<2.3.4",
"product_id": "CSAFPID-5965559"
}
}
],
"category": "product_name",
"name": "nginx-ui"
}
],
"category": "vendor",
"name": "0xJacky"
},
{
"branches": [
{
"branches": [
{
"category": "product_version_range",
"name": "vers:unknown/<2.3.4",
"product": {
"name": "vers:unknown/<2.3.4",
"product_id": "CSAFPID-5982828",
"product_identification_helper": {
"cpe": "cpe:2.3:a:nginxui:nginx_ui:*:*:*:*:*:*:*:*"
}
}
}
],
"category": "product_name",
"name": "nginx_ui"
}
],
"category": "vendor",
"name": "nginxui"
}
]
},
"vulnerabilities": [
{
"cve": "CVE-2026-33027",
"cwe": {
"id": "CWE-22",
"name": "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')"
},
"notes": [
{
"category": "description",
"text": "## Summary\nThe nginx-ui configuration improperly handles URL-encoded traversal sequences. When specially crafted paths are supplied, the backend resolves them to the base Nginx configuration directory and executes the operation on the base directory (/etc/nginx). In particular, this allows an authenticated user to remove the entire `/etc/nginx` directory, resulting in a partial Denial of Service.\n\n## Details\nThe file deletion logic fails to correctly validate and normalize paths containing URL-encoded traversal sequences such as `..%252F`.\n\nWhen such input is processed, the internal path resolution logic attempts to clamp the path into the allowed configuration directory. Instead of rejecting the traversal attempt, the clamping mechanism resolves the path to the base Nginx configuration directory itself.\n\nBecause the deletion handler invokes `os.RemoveAll`, which recursively removes directories, this results in the deletion of the entire `/etc/nginx` directory.\n\nThis behavior creates a dangerous interaction between path normalization and deletion logic:\n\n- Traversal sequences are not rejected.\n- Double-encoding (`..%252F`) is used to bypass initial shallow filters.\n- The clamping mechanism resolves malicious paths to the base configuration directory.\n- The deletion handler recursively deletes the resolved path.\n\nAs a result, an attacker can trigger deletion of the entire Nginx configuration directory instead of being blocked by path validation logic.\n\n### Root Cause\n\nThe vulnerability results from a combination of design flaws:\n\n- **Improper Path Canonicalization**: URL-encoded traversal sequences are not properly rejected.\n- **Unsafe Fallback Logic**: The `GetConfPath` clamping mechanism returns the base configuration directory when traversal is detected instead of rejecting the request.\n- **Unsafe Deletion Primitive**: The deletion handler invokes `os.RemoveAll`, which recursively deletes directories without additional safeguards. (delete.go)\n```\n\t// Delete the file or directory\n\terr = os.RemoveAll(fullPath)\n\tif err != nil {\n\t\tcosy.ErrHandler(c, err)\n\t\treturn\n\t}\n```\nThis interaction causes the deletion operation to target the most sensitive directory when a traversal attempt occurs.\n\n### Environment\n- **Server OS**: Kali Linux 6.17.10-1kali1 (6.17.10+kali-amd64)\n- **Nginx UI Version**: nginx-ui v2.3.3\n- **Deployment**: Docker / Default installation\n\n\n## Proof of Concept\n### Steps to Reproduce\n1. Log into nginx-ui.\n\n2. Go to Manage Configs and create a Folder named *..%252F..%252F..%252F..%252Ftest*\n![\"image\"](\"https://github.com/user-attachments/assets/738d7d65-7e13-48fa-affc-d5509c43900f\")
\n\n3. Observe that the backend resolves the path to /etc/nginx.. \n\n4. Now lets create a file called *testing*. \n\n5. Save it and rename it to *..%252F..%252F..%252F..%252Ftest* (It is not possible to create it directly with the payload name so we have to rename it)\n\n6. Go back to manage configs and Click Delete to remove the file we just created. \n\n7. Check that there is an error: \n![\"image\"](\"https://github.com/user-attachments/assets/51a36310-0676-4fe5-b80c-e0199498efbf\")
\n\n8. Reload the website and check that the /etc/nginx folder has been completely removed: \n![\"image\"](\"https://github.com/user-attachments/assets/0a9ddd1b-786b-4cf2-8abd-1dc6f3a77807\")
\n\n\n## Impact\n\nAn authenticated user capable of invoking the configuration deletion endpoint can trigger the recursive deletion of the entire Nginx configuration directory (`/etc/nginx`).\n\nThis results in:\n- Immediate failure of the Nginx service due to missing configuration files.\n- Loss of all Nginx configuration managed by nginx-ui.\n- Denial of Service for all web services relying on the affected Nginx instance.\n\nAs the deletion operation uses a recursive filesystem call, the entire configuration directory is removed, leaving the system unable to restart Nginx until the configuration is manually restored.\n\nA patched version is available at https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4.",
"title": "github - https://api.github.com/advisories/GHSA-m8p8-53vf-8357"
},
{
"category": "description",
"text": "Nginx UI is a web user interface for the Nginx web server. Prior to version 2.3.4, the nginx-ui configuration improperly handles URL-encoded traversal sequences. When specially crafted paths are supplied, the backend resolves them to the base Nginx configuration directory and executes the operation on the base directory (/etc/nginx). In particular, this allows an authenticated user to remove the entire /etc/nginx directory, resulting in a partial Denial of Service. This issue has been patched in version 2.3.4.",
"title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33027"
},
{
"category": "description",
"text": "Nginx UI is a web user interface for the Nginx web server. Prior to version 2.3.4, the nginx-ui configuration improperly handles URL-encoded traversal sequences. When specially crafted paths are supplied, the backend resolves them to the base Nginx configuration directory and executes the operation on the base directory (/etc/nginx). In particular, this allows an authenticated user to remove the entire /etc/nginx directory, resulting in a partial Denial of Service. This issue has been patched in version 2.3.4.",
"title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33027.json"
},
{
"category": "other",
"text": "0.00053",
"title": "EPSS"
},
{
"category": "other",
"text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
"title": "CVSSV4"
},
{
"category": "other",
"text": "6.9",
"title": "CVSSV4 base score"
},
{
"category": "other",
"text": "4.4",
"title": "NCSC Score"
},
{
"category": "other",
"text": "There is product data available from source Certbundde",
"title": "NCSC Score top increasing factors"
},
{
"category": "other",
"text": "Is related to (a version of) an uncommon product, There is exploit data available from source Nvd",
"title": "NCSC Score top decreasing factors"
}
],
"product_status": {
"known_affected": [
"CSAFPID-5965559",
"CSAFPID-5968318",
"CSAFPID-5982828"
]
},
"references": [
{
"category": "external",
"summary": "Source - github",
"url": "https://api.github.com/advisories/GHSA-m8p8-53vf-8357"
},
{
"category": "external",
"summary": "Source - nvd",
"url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33027"
},
{
"category": "external",
"summary": "Source - cveprojectv5",
"url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33027.json"
},
{
"category": "external",
"summary": "Source - certbundde",
"url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-0931.json"
},
{
"category": "external",
"summary": "Source - first",
"url": "https://api.first.org/data/v1/epss?limit=10000&offset=0"
},
{
"category": "external",
"summary": "Reference - cveprojectv5; github; nvd",
"url": "https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-m8p8-53vf-8357"
},
{
"category": "external",
"summary": "Reference - certbundde; cveprojectv5; github; nvd",
"url": "https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4"
},
{
"category": "external",
"summary": "Reference - certbundde; github",
"url": "https://github.com/advisories/GHSA-m8p8-53vf-8357"
},
{
"category": "external",
"summary": "Reference - github",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33027"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-0931.json"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-0931"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17151"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17152"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17154"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17156"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17158"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://euvd.enisa.europa.eu/enisa/EUVD-2026-17194"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://github.com/advisories/GHSA-5hf2-vhj6-gj9m"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://github.com/advisories/GHSA-cp8r-8jvw-v3qg"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://github.com/advisories/GHSA-fhh2-gg7w-gwpq"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://github.com/advisories/GHSA-h6c2-x2m2-mwhf"
},
{
"category": "external",
"summary": "Reference - certbundde",
"url": "https://github.com/advisories/GHSA-m468-xcm6-fxg4"
}
],
"scores": [
{
"cvss_v3": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"baseScore": 6.5,
"baseSeverity": "MEDIUM"
},
"products": [
"CSAFPID-5965559",
"CSAFPID-5968318",
"CSAFPID-5982828"
]
}
],
"title": "CVE-2026-33027"
}
]
}