CVE-2026-117666
ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary
- State
- Published
- Severity
- 9.1 Critical
- Published
- Oct 30, 2026
- Updated
- Oct 30, 2026
- Reserved
- Oct 30, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 9.1 Critical | 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 | EEF |
Weaknesses
- CWE-297 Improper Validation of Certificate with Host Mismatch
Affected Products
| Product | Versions |
|---|---|
ssl_verify_fundeadtrickster |
|
ssl_verify_fundeadtrickster |
|
References
- ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundaryvendor-advisoryrelated
- EEF CNA record for CVE-2026-117666related
- OSV record EEF-CVE-2026-117666related
- Do not let partial-label wildcards match across label boundaries (ssl_verify_fun.erl pull request #33)patch
- Introducing commit a49ca56 in deadtrickster/ssl_verify_fun.erlrelated
- Fix commit ca34031 in deadtrickster/ssl_verify_fun.erlpatch
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