{"id":"OSEC-2026-16","aliases":[],"status":"published","title":"Path traversal in Cohttp.Path.resolve_local_file","description":"The issue is that the function normalizes the URI path before percent\ndecoding it:\n\n```OCaml\nlet resolve_local_file ~docroot ~uri =\n\n  let path = Uri.(pct_decode (path (resolve \"http\" (of_string \"/\") uri))) in\n\n  ...\n```\n\nBecause `%2f` is decoded after Uri.resolve, encoded separators survive\ndot-segment normalization. For example, a request path like:\n\n```\n/static/..%2f..%2f..%2fetc/passwd\n```\n\nis normalized as a single encoded segment, then decoded into:\n\n```\n/static/../../../etc/passwd\n```\n\nafterwards.\n\n## Timeline\n\n- Aug 11th 2026: report to security@ocaml.org\n- Aug 14th 2026: PR published on \u003chttps://github.com/mirage/ocaml-cohttp/pull/1145\u003e\n- Aug 20th 2026: fix released in v6.3.0 \u003chttps://github.com/ocaml/opam-repository/pull/30528\u003e","severity":{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/S:N/AU:Y/R:A/V:D/RE:M","level":"high","from":"osv"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"published":"2026-08-20T18:15:00Z","modified":"2026-11-06T13:45:03Z","fixes":[{"ecosystem":"opam","package":"cohttp","fixed_in":["6.3.0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"opam","package":"cohttp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.3.0"}]}],"versions":["0.9.1","0.9.2","0.9.3","0.9.4","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9","0.9.10","0.9.11","0.9.12","0.9.13","0.9.14","0.9.15","0.9.16","0.10.0","0.10.1","0.11.0","0.11.1","0.11.2","0.12.0","0.13.0","0.14.0","0.15.0","0.15.1","0.15.2","0.16.0","0.16.1","0.17.0","0.17.1","0.17.2","0.18.0","0.18.1","0.18.2","0.18.3","0.19.0","0.19.1","0.19.2","0.19.3","0.20.0","0.20.1","0.20.2","0.21.0","0.21.1","0.22.0","0.99.0","1.0.0","1.0.2","1.1.0","1.1.1","1.2.0","2.0.0","2.1.2","2.1.3","2.2.0","2.3.0","2.4.0","2.5.0","2.5.1","2.5.2","2.5.2-1","2.5.3","2.5.4","2.5.5","2.5.6","2.5.7","2.5.8","3.0.0","4.0.0","4.1.1","4.1.2","5.0.0","5.1.0","5.2.0","5.3.0","5.3.1","6.0.0~alpha0","6.0.0~alpha1","6.0.0~alpha2","6.0.0~beta2","6.0.0","6.1.0","6.1.1","6.2.1","6.2.2"]}],"sources":{"osv":[{"id":"OSEC-2026-16","title":"Path traversal in Cohttp.Path.resolve_local_file","description":"The issue is that the function normalizes the URI path before percent\ndecoding it:\n\n```OCaml\nlet resolve_local_file ~docroot ~uri =\n\n  let path = Uri.(pct_decode (path (resolve \"http\" (of_string \"/\") uri))) in\n\n  ...\n```\n\nBecause `%2f` is decoded after Uri.resolve, encoded separators survive\ndot-segment normalization. For example, a request path like:\n\n```\n/static/..%2f..%2f..%2fetc/passwd\n```\n\nis normalized as a single encoded segment, then decoded into:\n\n```\n/static/../../../etc/passwd\n```\n\nafterwards.\n\n## Timeline\n\n- Aug 11th 2026: report to security@ocaml.org\n- Aug 14th 2026: PR published on \u003chttps://github.com/mirage/ocaml-cohttp/pull/1145\u003e\n- Aug 20th 2026: fix released in v6.3.0 \u003chttps://github.com/ocaml/opam-repository/pull/30528\u003e","status":"published","published":"2026-08-20T18:15:00Z","modified":"2026-11-06T13:45:03.048919117Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/S:N/AU:Y/R:A/V:D/RE:M","level":"high"}],"updated_at":"2026-11-06T14:15:37.916691Z"}]}}