Custom cacerts or cacertfile do not restrict trust to the pinned CA in hackney
En bref
Sévérité
CRITICAL 9.1
EPSS
EPSS 0.27 % · centile 19 (2026-10-27)
État
PUBLISHED
Publiée
Mise à jour
Attribuée par
EEF
Statut NVD
Awaiting Analysis
Description
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. 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.
The hostname check still applies, so the attacker needs a publicly trusted certificate for the pinned hostname.
This issue affects hackney: from 1.24.0 before 4.9.0.
