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CVE Vulnerabilities

CVE-2026-3833

Improper Handling of Case Sensitivity

Published: Apr 30, 2026 | Modified: Jun 17, 2026
CVSS 3.x
7.4
HIGH
Source:
NVD
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 2.x
RedHat/V2
RedHat/V3
6.5 MODERATE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2026-3833
CWEhttps://cwe.mitre.org/data/definitions/178.html

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of nameConstraints labels, specifically for dNSName (DNS) or rfc822Name (email) constraints within excludedSubtrees or permittedSubtrees. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.

Weakness

The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.

Affected Software

NameVendorStart VersionEnd Version
GnutlsGnu- (including)- (including)
Hardened_imagesRedhat- (including)- (including)
Openshift_container_platformRedhat4.0 (including)4.0 (including)
Enterprise_linuxRedhat6.0 (including)6.0 (including)
Enterprise_linuxRedhat7.0 (including)7.0 (including)
Enterprise_linuxRedhat8.0 (including)8.0 (including)
Enterprise_linuxRedhat9.0 (including)9.0 (including)
Enterprise_linuxRedhat10.0 (including)10.0 (including)
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 Hardened ImagesRedHatgnutls-main-3.8.13-1.hum1*
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

Improperly handled case sensitive data can lead to several possible consequences, including:

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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