osec-2026-16
CVSS 8.7 osv_ocaml
Description
The issue is that the function normalizes the URI path before percent decoding it: ```OCaml let resolve_local_file ~docroot ~uri = let path = Uri.(pct_decode (path (resolve "http" (of_string "/") uri))) in ... ``` Because `%2f` is decoded after Uri.resolve, encoded separators survive dot-segment normalization. For example, a request path like: ``` /static/..%2f..%2f..%2fetc/passwd ``` is normalized as a single encoded segment, then decoded into: ``` /static/../../../etc/passwd ``` afterwards. ## Timeline - Aug 11th 2026: report to security@ocaml.org - Aug 14th 2026: PR published on <https://github.com/mirage/ocaml-cohttp/pull/1145> - Aug 20th 2026: fix released in v6.3.0 <https://github.com/ocaml/opam-repository/pull/30528>
Timeline
- Published
- unknown
- Last Modified
- unknown
CVSS Details
CVSS details not available.
Affected Products
No product information available.
Weaknesses (CWE)
References
No references available.
Linked Vulnerabilities
No linked vulnerabilities found.
{
"affected": [
{
"database_specific": {
"source": "https://github.com/ocaml/security-advisories/blob/generated-osv/2026/OSEC-2026-16.json"
},
"ecosystem_specific": {
"affected_bindings": [
"Cohttp.Path.resolve_local_file",
"Cohttp_async.Server.resolve_local_file",
"Cohttp_lwt_unix.Server.resolve_file",
"Cohttp_lwt.Make().resolve_local_file"
],
"opam_constraint": "cohttp {< \"6.3.0\"}"
},
"package": {
"ecosystem": "opam",
"name": "cohttp",
"purl": "pkg:opam/cohttp"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "6.3.0"
}
],
"type": "ECOSYSTEM"
},
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5f5a65ec3289c1cd8072bdf0ef22c181b4f11356"
}
],
"repo": "https://github.com/mirage/ocaml-cohttp.git",
"type": "GIT"
}
],
"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",
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"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",
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"2.1.3",
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"2.3.0",
"2.4.0",
"2.5.0",
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"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",
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"6.2.1",
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"v2.1.3",
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"v2.1.0-cohttp-mirage",
"v1.2.0",
"v1.1.1",
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"v1.0.2",
"v1.0.1",
"v1.0.0",
"v0.99.0",
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"v0.21.1",
"v0.21.0",
"v0.20.1",
"v0.20.0",
"v0.19.3",
"v0.19.2",
"v0.19.1",
"v0.19.0",
"v0.18.3",
"v0.18.2",
"v0.18.0",
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"v0.17.1",
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"v0.15.1",
"v.0.15.1",
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"v0.14.0",
"v0.13.0",
"v0.12.0",
"v0.11.2",
"v0.11.1",
"v0.11.0",
"v0.9.15",
"v0.9.14",
"v0.9.13",
"v0.9.12",
"v0.9.11",
"ocaml-cohttp-0.9.10",
"ocaml-cohttp-0.9.7",
"ocaml-cohttp-0.9.5",
"ocaml-cohttp-0.9.4",
"ocaml-cohttp-0.9.3",
"ocaml-cohttp-0.9.2",
"ocaml-cohttp-0.9.1"
]
}
],
"credits": [
{
"name": "Sapphire Livingstone",
"type": "REPORTER"
},
{
"name": "Sapphire Livingstone",
"type": "REMEDIATION_DEVELOPER"
},
{
"name": "Anil Madhavapeddy",
"type": "REMEDIATION_DEVELOPER"
},
{
"name": "Anil Madhavapeddy",
"type": "REMEDIATION_REVIEWER"
},
{
"name": "Michael Dales",
"type": "REMEDIATION_REVIEWER"
},
{
"name": "Edwin Torok",
"type": "REMEDIATION_REVIEWER"
},
{
"name": "Patrick Ferris",
"type": "REMEDIATION_REVIEWER"
},
{
"name": "Hannes Mehnert",
"type": "COORDINATOR"
}
],
"database_specific": {
"cwe": [
"CWE-22"
],
"human_link": "https://github.com/ocaml/security-advisories/tree/main/advisories/2026/OSEC-2026-16.md",
"osv": "https://github.com/ocaml/security-advisories/tree/generated-osv/2026/OSEC-2026-16.json"
},
"details": "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 <https://github.com/mirage/ocaml-cohttp/pull/1145>\n- Aug 20th 2026: fix released in v6.3.0 <https://github.com/ocaml/opam-repository/pull/30528>",
"id": "OSEC-2026-16",
"modified": "2026-08-22T11:15:03.544179774Z",
"published": "2026-08-20T18:15:00Z",
"schema_version": "1.9.0",
"severity": [
{
"score": "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",
"type": "CVSS_V4"
}
],
"summary": "Path traversal in Cohttp.Path.resolve_local_file"
}