{"id":"CVE-2026-66064","aliases":["GHSA-964w-f6gj-5236","GO-2026-6134"],"url":"https://o3.security/vulnerability/CVE-2026-66064","summary":"goshs has ACL Bypass & Path Traversal","details":"## Summary\n\n`sendFile` derives the served filename from the raw request path while opening the file from the cleaned path, so appending a trailing slash empties the derived name and defeats both the never-serve rule for the ACL file and the block list. \n\n## Finding (Medium): trailing-slash ACL and hidden-file bypass\n\nhttpserver/handler.go, sendFile (lines 789-801) takes the filename from the RAW req.URL.Path while the file itself is opened from the filepath.Clean-ed path. The two disagree, and a trailing slash makes the derived name the empty string. Both protections key on that derived name, so both are defeated: the rule that never serves the .goshs ACL file, and the acl.Block list.\n\nMeasured, with negative controls:\n\n```\nGET /blocked/secret.txt    -> 404          (control, correctly blocked)\nGET /blocked/secret.txt/   -> 200 + contents\nGET /blocked/.goshs/       -> 200, returns the ACL file itself,\n                              including the admin:$2a$... bcrypt hash\n```\n\nUnauthenticated when the ACL is configured block-only (common usage). Stated precisely: AUTHENTICATION IS NOT BYPASSED. An unauthenticated request against a directory protected by authentication still returns 401 under the same trick; I tested that. The claim is specifically that the block list and the ACL-file protection are bypassed. In-tree evidence that sendFile is the defect: the sibling handlers doDir and bulkDownload both derive the name correctly; sendFile is the lone outlier.\n\n## Suggested fixes\n\n1. Derive the served filename from the same cleaned path used to open the file, so the authorization decision and the file access cannot disagree.\n\n## Tooling\n\nAI assistance was used while investigating. The finding was reproduced against a running server on loopback with negative controls, including the 404-versus-200 pair and the authenticated-directory control that shows authentication is not affected.","published":"2026-07-28T22:12:04.830Z","modified":"2026-10-25T02:30:21.052758071Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":{"score":0.00308,"percentile":0.23557,"asOf":"2026-09-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/patrickhener/goshs/v2","fixedVersion":"2.1.5-0.20260727065949-f3ef599e4091"},{"ecosystem":"Go","name":"goshs.de/goshs/v2","fixedVersion":"2.1.5-0.20260727065949-f3ef599e4091"},{"ecosystem":"Go","name":"github.com/patrickhener/goshs","fixedVersion":null},{"ecosystem":"Go","name":"goshs.de/goshs","fixedVersion":null}],"fix":{"url":"https://github.com/goshs-labs/goshs/commit/f3ef599e409151d1380866e47de8b1afb0bb54fa","label":"goshs-labs/goshs@f3ef599"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66064.json"},{"type":"ADVISORY","url":"https://github.com/goshs-labs/goshs/security/advisories/GHSA-964w-f6gj-5236"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66064"},{"type":"FIX","url":"https://github.com/goshs-labs/goshs/commit/f3ef599e409151d1380866e47de8b1afb0bb54fa"},{"type":"FIX","url":"https://github.com/goshs-labs/goshs/pull/222"},{"type":"PACKAGE","url":"https://github.com/goshs-labs/goshs"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-25T02:30:21.052758071Z"}}