CVE-2026-42013: gnutls · Improper Certificate Validation
Affects gnutlsSource CVE Database V5
Not known to be exploited · CVSS 8.2 High.
Data as of 30 Oct 2026, 12:04 UTC
Thin evidence
One scorer or none| CNA (redhat) | CVSS 3.1 | 8.2 |
|---|
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 26 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| gnutls | Affected
| Fixed in– |
Description
A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.
References
- access.redhat.com/errata/RHSA-2026:13274 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:20611 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:20612 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:20613 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:26319 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:26409 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:29197 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:30004 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:30849 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:30850 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:32962 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:33125 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:40762 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:41921 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:43575 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-42013 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2467448 (opens in a new tab)
- gnutls.org/security-new.html (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:58981 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:57483 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:56853 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:59831 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:60019 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:72502 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:74674 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82304 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82322 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82347 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82354 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82372 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82857 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:82888 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:89197 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:89232 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:89333 (opens in a new tab)