GnuTLS improper validation of specified quantity in input

Summaryinfo

A vulnerability, which was classified as problematic, was found in GnuTLS. This impacts an unknown function. Executing a manipulation can lead to improper validation of specified quantity in input. This vulnerability is handled as CVE-2026-42013. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability has been found in GnuTLS (affected version not known) and classified as problematic. This vulnerability affects some unknown functionality. The manipulation with an unknown input leads to a improper validation of specified quantity in input vulnerability. The CWE definition for the vulnerability is CWE-1284. The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2026-42013 since 04/23/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/20/2026).

The vulnerability scanner Nessus provides a plugin with the ID 316551 (Debian dla-4595 : gnutls-bin - security update), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (316551) and CERT Bund (WID-SEC-2026-1312). Once again VulDB remains the best source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• IBM MQ
• Microsoft Azure Linux
• Open Source GnuTLS

Productinfo

Type

• Network Encryption Software

Name

• GnuTLS

License

• open-source

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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