{"id":"CVE-2026-115693","title":"Custom cacerts or cacertfile do not restrict trust to the pinned CA in hackney","summary":"Improper Certificate Validation vulnerability in hackney_ssl in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. ha…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","cvssSource":"cna","cwe":["CWE-295"],"vendor":"benoitc","product":"hackney","affected":["hackney >= 1.24.0 < 4.9.0","benoitc/hackney >= d8a9afcf5c3849904274e2eba1df56c63d1a1a0c < 915eb5737e9c489d8fc22eec8cdae30e9b027be4"],"published":"2026-10-26","updated":"2026-10-26","sourceUpdated":"2026-10-26T13:49:29.374Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-115693","references":[{"url":"https://github.com/benoitc/hackney/pull/978","label":"Drop the certifi partial_chain when the caller pins cacerts or cacertfile (benoitc/hackney#978)"},{"url":"https://cna.erlef.org/cves/CVE-2026-115693.html","label":"EEF CNA record for CVE-2026-115693"},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-115693","label":"OSV record EEF-CVE-2026-115693"},{"url":"https://github.com/benoitc/hackney/releases/tag/4.9.0","label":"hackney 4.9.0 release notes"},{"url":"https://github.com/benoitc/hackney/commit/d8a9afcf5c3849904274e2eba1df56c63d1a1a0c","label":"Introducing commit d8a9afc in benoitc/hackney"},{"url":"https://github.com/benoitc/hackney/commit/915eb5737e9c489d8fc22eec8cdae30e9b027be4","label":"Fix commit 915eb57 in benoitc/hackney"}],"tags":["cve.org"],"ingestedAt":"2026-10-26T14:27:31.815Z","slug":"CVE-2026-115693","body":"## Overview\n\nImproper Certificate Validation vulnerability in hackney_ssl in benoitc hackney allows an on-path attacker to impersonate a server pinned to a private certificate authority via a certificate chain that ends in a publicly trusted root. hackney adds {partial_chain, fun hackney_ssl:partial_chain/1} to every verify_peer configuration. The callback returns any certificate in the peer chain whose public key matches a root in the bundled certifi store as the trust anchor, and OTP honours that callback over the configured cacerts. hackney_ssl:merge_ssl_opts/3 kept the callback when the caller replaced the trust store with cacerts or cacertfile in ssl_options, so a connection pinned to a private CA still accepted any chain that carried a publicly trusted root.\n\nThe hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname.\n\nThis issue affects hackney: from 1.24.0 before 4.9.0.\n\n## Affected\n\n- `hackney >= 1.24.0 < 4.9.0`\n- `benoitc/hackney >= d8a9afcf5c3849904274e2eba1df56c63d1a1a0c < 915eb5737e9c489d8fc22eec8cdae30e9b027be4`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n### Workarounds\n\nPass your own {partial_chain, Fun} in ssl_options alongside cacerts or cacertfile. A caller-supplied partial_chain replaces hackney's in the merge, and a callback that returns unknown_ca makes OTP validate against the configured cacerts only.","depth":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}