CVE-2026-117666
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
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
Exploit Intelligence
Low risk: more likely to be exploited than 9% of all known CVEs.
References
Related Vulnerabilities
Other CWE-297 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2014-3522 | Medium | 4.0 | 5.6% | - | Fix |
| CVE-2018-10936 | High | 8.1 | 2.9% | - | Fix |
| CVE-2020-1887 | Critical | 9.1 | 1.6% | - | Fix |
| CVE-2024-2466 | Medium | 6.5 | 1.5% | - | Fix |
| CVE-2020-14387 | High | 7.4 | 1.1% | - | Fix |
| CVE-2020-15260 | Medium | 6.8 | 1.0% | - | Fix |
Common questions
How do I fix CVE-2026-117666?
No published fix for CVE-2026-117666 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-117666 being actively exploited?
Not that we know of. CVE-2026-117666 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.19% is the estimated probability that it will be exploited in the next 30 days. That is higher than 9% of all scored CVEs.
How severe is CVE-2026-117666?
CVE-2026-117666 has a CVSS v4 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-10-30.