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CVE-2026-117666: ssl_verify_fun may accept wrong wildcard certificates

CVE-2026-117666 · published 5 days ago

Summary

The ssl_verify_fun library can treat a certificate with a partial wildcard (like f*.example.net) as valid for other names such as f.evil.example.net. This can let an attacker pretend to be a trusted server or client if SNI is disabled or custom hostname checks are used. Update the library to version 1.1.8 or later, or disable the custom verification and rely on the built‑in checks.

What to do

Update deadtrickster ssl_verify_fun to version 1.1.8.
Update ssl_verify_fun to version 1.1.8.

Affected software

Ecosystem	Vendor	Product	Affected versions
Debian:12	debian	rebar3	All versions
–	deadtrickster	ssl_verify_fun	< 1.1.8 < ca34031299cd2e0c98794c0da4ba556b94e39aad
Hex	deadtrickster	ssl_verify_fun	>= 1.0.1, < 1.1.8 Fix: upgrade to 1.1.8
Hex	–	ssl_verify_fun	>= 1.0.1, < 1.1.8 Fix: upgrade to 1.1.8

Original advisory text

ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary

Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. try_match_wildcard/4 in src/ssl_verify_hostname.erl anchors only the text before and after the * of an identifier such as f*.example.net, so the wildcard also consumes dots and the certificate is accepted for f.evil.example.net. RFC 6125 confines a wildcard to the left-most label. The same matcher lets *.168.1.1 match the IP literal 192.168.1.1. Whole-label wildcards are matched correctly. Erlang/OTP 20.0 and later check the hostname in ssl before a user verify_fun sees valid_peer, so a client that keeps server_name_indication set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of verify_cert_hostname/2. This issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.

References

https://cna.erlef.org/cves/CVE-2026-117666.html URL
https://github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw... Vendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-117666 URL
https://hex.pm/packages/ssl_verify_fun Product
https://github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a39816... Patch
https://github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794... Patch
https://github.com/deadtrickster/ssl_verify_fun.erl/pull/33 Patch
https://github.com URL
https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/117xxx/CVE-2026-1176... Vendor Advisory
https://github.com/deadtrickster/ssl_verify_fun.erl Product
https://nvd.nist.gov/vuln/detail/CVE-2026-117666 Vendor Advisory
https://repo.hex.pm URL
https://security-tracker.debian.org/tracker/CVE-2026-117666 Vendor Advisory

Severity

8.6 High

Exploitation

<1% chance of attack within 30 days

Type

CWE-297Improper Validation of Certificate with Host Mismatch

Timeline

Published30 Oct 2026

Updated4 Nov 2026

First seen30 Oct 2026

Sources

CVE-2026-117666 · NVD

CVE-2026-117666 · MITRE

EEF-CVE-2026-117666 · OSV

GHSA-7gw2-hphm-c5px · GHSA

CVE-2026-117666 · OSV

DEBIAN-CVE-2026-117666 · OSV

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