CVE-2026-42010 Gnutls: gnutls: authentication bypass via nul character in username
Remote attackers can bypass authentication in GnuTLS servers using RSA-PSK by exploiting NUL character handling in usernames.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42010?
CVE-2026-42010 is a high-severity authentication bypass vulnerability in Gnu Gnutls, published on 7 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
A flaw was found in gnutls. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) wrongfully matched usernames containing a NUL character with truncated usernames. A remote attacker could exploit this by sending a specially crafted username, leading to an authentication bypass. This vulnerability allows an attacker to gain unauthorized access by circumventing the authentication process.
Which versions are affected by CVE-2026-42010?
It affects 4 products.
Products include Gnu Gnutls, Redhat Enterprise Linux, Redhat Hardened Images, Redhat Openshift Container Platform.
How do I fix CVE-2026-42010?
Apply the vendor's patch.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-42010 being exploited?
There is no known exploitation of CVE-2026-42010 in the wild and no public exploit code.
Other vulnerabilities in Gnu Gnutls
Sources
Also known as ALPINE-CVE-2026-42010, AZL-86775, BELL-CVE-2026-42010, CLSA-2026-1778934026, CLSA-2026-1779183792, CLSA-2026-1779272835 and 6 more.