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Misconfiguration
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CVE Vulnerabilities

CVE-2026-42013

Improper Validation of Specified Quantity in Input

Published: May 26, 2026 | Modified: Jun 17, 2026
CVSS 3.x
N/A
Source:
NVD
CVSS 2.x
RedHat/V2
RedHat/V3
8.2 MODERATE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2026-42013
CWEhttps://cwe.mitre.org/data/definitions/1284.html

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.

Weakness

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.

Affected Software

NameVendorStart VersionEnd Version
Red Hat Enterprise Linux 10RedHatgnutls-0:3.8.10-4.el10_2*
Red Hat Enterprise Linux 10.0 Extended Update SupportRedHatgnutls-0:3.8.9-9.el10_0.19*
Red Hat Enterprise Linux 8RedHatgnutls-0:3.6.16-8.el8_10.6*
Red Hat Enterprise Linux 8RedHatgnutls-0:3.6.16-8.el8_10.6*
Red Hat Enterprise Linux 9RedHatgnutls-0:3.8.10-4.el9_8*
Red Hat Enterprise Linux 9RedHatgnutls-0:3.8.10-4.el9_8*
Red Hat Update Infrastructure 5RedHatrhui5/cds-rhel9:1781525684*
Red Hat Update Infrastructure 5RedHatrhui5/haproxy-rhel9:1781525671*
Red Hat Update Infrastructure 5RedHatrhui5/installer-rhel9:1781525693*
Red Hat Update Infrastructure 5RedHatrhui5/rhua-rhel9:1781525739*
Gnutls28Ubuntudevel*
Gnutls28Ubuntuesm-infra/xenial*
Gnutls28Ubuntufips-preview/jammy*
Gnutls28Ubuntufips-updates/jammy*
Gnutls28Ubuntufips-updates/noble*
Gnutls28Ubuntujammy*
Gnutls28Ubuntunoble*
Gnutls28Ubuntuquesting*
Gnutls28Ubunturesolute*
Gnutls28Ubuntuupstream*

Extended Description

Specified quantities include size, length, frequency, price, rate, number of operations, time, and others. Code may rely on specified quantities to allocate resources, perform calculations, control iteration, etc.

Potential Mitigations

  • Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
  • When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
  • Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

References

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