{"id":"CVE-2026-48126","aliases":["GHSA-jc3j-x6pg-4hmv","GO-2026-5460"],"url":"https://o3.security/vulnerability/CVE-2026-48126","summary":"Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent dir","details":"Algernon is a small self-contained pure-Go web server. Prior to 1.17.8, when algernon is started with --domain (or --letsencrypt, which silently turns on --domain at engine/flags.go:372), the request handler resolves the served directory by joining the configured --dir with the value of the client-supplied Host header. The join is performed by filepath.Join with no validation, so a Host: .. header walks one level above the document root. Subsequent file resolution then exposes everything in that parent directory — arbitrary file read, full directory listing, and, if any .lua file is present, server-side Lua execution. This vulnerability is fixed in 1.17.8.","published":"2026-05-26T16:44:09.104Z","modified":"2026-08-12T03:51:31.191065070Z","cvss":{"score":8.2,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N"},"epss":{"score":0.00335,"percentile":0.26338,"asOf":"2026-09-08"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/xyproto/algernon","fixedVersion":"1.17.8"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48126.json"},{"type":"ADVISORY","url":"https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48126"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:31.191065070Z"}}