{"cve":"CVE-2026-48126","nvd":{"published":"2026-05-26T17:16:53.360","modified":"2026-07-24T11:10:00.170","status":"Deferred","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","score":8.2},"cwes":["CWE-22","CWE-23","CWE-644"],"references":["https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv","https://github.com/xyproto/algernon/security/advisories/GHSA-jc3j-x6pg-4hmv"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:36:28.938604137+00:00"},"epss":{"cve":"CVE-2026-48126","score":0.00335,"percentile":0.2692,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-jc3j-x6pg-4hmv","url":"https://osv.dev/vulnerability/GHSA-jc3j-x6pg-4hmv","summary":"Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent dir","modified":"2026-06-25T23:11:41.944267819Z","packages":[{"ecosystem":"Go","name":"github.com/xyproto/algernon","purl":"pkg:golang/github.com/xyproto/algernon","ranges":["<1.17.8"],"fixed":["1.17.8"]}]},{"id":"GO-2026-5460","url":"https://osv.dev/vulnerability/GO-2026-5460","summary":"Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent dir in github.com/xyproto/algernon","modified":"2026-06-25T23:01:10.808891348Z","packages":[{"ecosystem":"Go","name":"github.com/xyproto/algernon","purl":"pkg:golang/github.com/xyproto/algernon","ranges":["<1.17.8"],"fixed":["1.17.8"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}