Partial wildcard certificates match wrong hosts in ssl_verify_fun
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
The deadtrickster ssl_verify_fun library from 1.0.1 before 1.1.8 accepts partial-label wildcard certificates for hosts they should not match (CWE-297). A certificate for f*.example.net is accepted for f.evil.example.net because the wildcard also consumes dots. An adversary in the middle can impersonate a TLS peer with such a certificate, but clients that keep SNI enabled still reject the mismatch, so exposure is limited to clients that disable SNI and servers that verify client certificate hostnames with this library.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| deadtrickster | ssl_verify_fun | 1.0.1 to before 1.1.8 | 1.1.8 | Patch available | CNA |
- ssl_verify_fun Vendordeadtrickster Affected 1.0.1 to before 1.1.8 Fixed in 1.1.8 Patch available CNA
CPE names CNA · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:* | — | — | deadtrickster |
- cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:* Versions — — ·deadtrickster
Remediation
Update ssl_verify_fun to version 1.1.8, which fixes the flaw.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA ssl_verify_fun (deadtrickster) Fixed in 1.1.8
Vendor assessments
Timeline
- 2026-10-30 Threatist record created from CVE-2026-117666
- 2026-11-01 Priority changed: MEDIUM → LOW
- 2026-11-03 Affected versions changed · Red Hat
- 2026-11-03 CVSS score added · Red Hat
- 2026-11-06 CISA SSVC decision points changed
- 2026-11-06 Priority changed: LOW → MEDIUM
References
Patch 2
Advisory 1
Sources
- CVE-2026-117666 · CVE Program
- CVE-2026-117666 · NVD
- FIRST EPSS
- CVE-2026-117666 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences