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CriticalVulnerabilityCVE-2026-117666updated 30 Oct 2026, 21:20 UTC

ssl_verify_fun accepts certificates for the wrong hostname

A library that checks who a secure connection is really talking to can be fooled by a special certificate, letting an attacker in the middle pose as the real server. Normal setups are protected, but some are not.

Fixed in ssl_verify_fun 1.1.8 or later · out Official source
SeverityCriticalCVSS 9.1 of 10
Being exploited?UnclearNo reports either way yet
Fix available?Yesssl_verify_fun 1.1.8 or later · since 30 Oct 2026
How sure is this?Official sourceBacked by an official source

How the attack works simplified

  1. 1Attacker in the middleIntercepts the connection to the server
  2. 2Crafted certificateWildcard like f*.example.net
  3. 3Hostname check passesWildcard matches across dots
  4. 4Impersonation succeedsClient trusts the wrong peer
  5. ResultAttacker impersonates a TLS peer

What happened

In ssl_verify_fun (Erlang), the hostname matcher try_match_wildcard/4 lets a partial-label wildcard such as f*.example.net match across dots, and lets *.168.1.1 match the IP 192.168.1.1, violating RFC 6125.

Why it is dangerous: An attacker who can intercept traffic and present a crafted certificate can impersonate a TLS peer, potentially reading or altering data sent to it. Clients that disable SNI, servers verifying client certificate hostnames, and code calling verify_cert_hostname/2 directly are exposed.

Are you affected?

You are affected if you run ssl_verify_fun from 1.0.1 before 1.1.8 and use it with SNI disabled, verify client certificate hostnames with it, or call verify_cert_hostname/2 directly.

ssl_verify_fun from 1.0.1 before 1.1.8

What to do

  1. Upgrade ssl_verify_fun to version 1.1.8 or later
  2. Confirm that clients keep server_name_indication set, which blocks this mismatch in Erlang/OTP 20.0 and later
  3. Review any direct calls to verify_cert_hostname/2 and any server-side client certificate hostname checks

Timeline

  1. 30 Oct 2026, 21:16 UTC
    Publicly disclosed
  2. 30 Oct 2026, 21:16 UTC
    Reported by NVD · NVD
  3. 30 Oct 2026, 21:20 UTC
    Picked up by Zero Radar

Sources 1 report, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-117666
CVSS
9.1 / 10
Disclosed
30 Oct 2026, 21:16 UTC
On Zero Radar
30 Oct 2026, 21:20 UTC (4 min after disclosure)
Last change
30 Oct 2026, 21:20 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

ssl_verify_fun accepts certificates for the wrong hostname · Zero Radar