GnuTLS SAN Size ForkCheck Bypass
CVE-2026-42013 Published on May 26, 2026
Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name
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.
Vulnerability Analysis
CVE-2026-42013 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a high impact on integrity, and no impact on availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
Improper Validation of Specified Quantity in Input
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.
Products Associated with CVE-2026-42013
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