CVE-2026-115693: Cert Validation Flaw

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.

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Weakness Type (CWE)

CWE-295 CWE-295

References

Other References

https://cna.erlef.org/cves/CVE-2026-115693.html https://github.com/benoitc/hackney/commit/915eb5737e9c489d8fc22eec8cdae30e9b027be4 https://github.com/benoitc/hackney/commit/d8a9afcf5c3849904274e2eba1df56c63d1a1a0c https://github.com/benoitc/hackney/pull/978 https://github.com/benoitc/hackney/releases/tag/4.9.0 https://osv.dev/vulnerability/EEF-CVE-2026-115693

Frequently Asked Questions

What is CVE-2026-115693? +

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.

How do I check if I'm vulnerable to CVE-2026-115693? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-115693