CVE-2026-42013
Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name
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.
INFO
Published Date :
May 26, 2026, 10:16 p.m.
Last Modified :
June 2, 2026, 4:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-42013
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 53f830b8-0a3f-465b-8143-3b8a9948e749 | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update GnuTLS to the latest version.
- Apply vendor security patches.
- Ensure certificate validation logic is robust.
Public PoC/Exploit Available at Github
CVE-2026-42013 has a 2 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-42013.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-42013 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-42013
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Aisle CVEs
ollama based on v0.36.0 - fixed all CVE
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-42013 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-42013 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Jun. 02, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:20612 -
CVE Modified by [email protected]
Jun. 01, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:20613 -
CVE Modified by [email protected]
May. 27, 2026
Action Type Old Value New Value Added Reference https://access.redhat.com/errata/RHSA-2026:20611 -
New CVE Received by [email protected]
May. 26, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N Added CWE CWE-1284 Added Reference https://access.redhat.com/security/cve/CVE-2026-42013 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2467448