Executive brief
A security flaw was found in GnuTLS, a widely used library that provides secure communication for applications and servers. When a server is configured to use a specific type of secure key (RSA-PSK), it may incorrectly validate usernames that contain special hidden characters. This could allow an unauthorized person to bypass the login process and gain access to the system without a valid password.
Technical details
A vulnerability classified as a Null Byte Interaction Error (CWE-626) exists in GnuTLS. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) incorrectly match usernames containing a NUL character with truncated versions of those usernames. This occurs because the comparison logic fails to validate the full length of the username string, stopping at the NUL byte. A remote, unauthenticated attacker can exploit this by sending a crafted username to bypass authentication mechanisms. Red Hat has released patches for various Enterprise Linux versions (8, 9, and 10) to address this by ensuring comparisons are performed up to the full username length.
Affected products
- GNU GnuTLS versions prior to 3.8.13-1
- Red Hat Enterprise Linux 8 8.10
- Red Hat Enterprise Linux 9 9.0
- Red Hat Enterprise Linux 10 10.0
- Red Hat Hardened Images -
Timeline
- 2026-05-02: advisory: Initial Red Hat security advisory RHSA-2026:13274 issued
- 2026-05-07: disclosed: CVE-2026-42010 published to NVD
- 2026-05-26: patched: Red Hat released updated packages for RHEL 8, 9, and 10