ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary
Summary
| CVE | CVE-2026-117666 |
|---|---|
| State | PUBLISHED |
| Assigner | EEF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-30 21:16:51 UTC |
| Updated | 2026-11-02 19:35:33 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 9.1 CRITICAL from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.001900000 probability, percentile 0.086390000 (date 2026-11-02)
Problem Types: CWE-297 | CWE-297 CWE-297 Improper Validation of Certificate with Host Mismatch
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | Secondary | 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/E:X/C... |
| 4.0 | CNA | CVSS | 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 |
CVSS v4.0 Breakdown
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Deadtrickster | Ssl Verify Fun | affected 1.0.1 1.1.8 semver | Not specified |
| CNA | Deadtrickster | Ssl Verify Fun | affected a49ca56923356c7a3981692b23c42ef32c2990e0 ca34031299cd2e0c98794c0da4ba556b94e39aad git | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a39816... | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw... | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794... | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| osv.dev/vulnerability/EEF-CVE-2026-117666 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | osv.dev | |
| github.com/deadtrickster/ssl_verify_fun.erl/pull/33 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| cna.erlef.org/cves/CVE-2026-117666.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | cna.erlef.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Andrew Moore (en)
CNA: Martin Karrer (en)
CNA: Andrew Moore (en)
CNA: Martin Karrer (en)
CNA: deadtrickster (en)
CNA: Jonatan Männchen / EEF (en)
Additional Advisory Data
Workarounds
CNA: On Erlang/OTP 21 or later, keep server_name_indication set to the target hostname and pass {customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]} in the ssl options. The hostname check in ssl then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options.