GnuTLS DTLS Handshake Fragment Reassembly merge_handshake_packet message_length length parameter

Summaryinfo

A vulnerability was found in GnuTLS and classified as problematic. This impacts the function merge_handshake_packet of the component DTLS Handshake Fragment Reassembly Handler. Executing a manipulation of the argument message_length can lead to length parameter. This vulnerability is tracked as CVE-2026-33846. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in GnuTLS (the affected version is unknown). It has been declared as problematic. This vulnerability affects the function merge_handshake_packet of the component DTLS Handshake Fragment Reassembly Handler. The manipulation of the argument message_length with an unknown input leads to a length parameter vulnerability. The CWE definition for the vulnerability is CWE-130. The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data. As an impact it is known to affect availability. CVE summarizes:

A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the message_length field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.

The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2026-33846 since 03/24/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 312106 (CentOS 9 : gnutls-3.8.10-4.el9), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (312106) and CERT Bund (WID-SEC-2026-1312). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• IBM MQ
• Microsoft Azure Linux
• Open Source GnuTLS
• Red Hat OpenShift

Productinfo

Type

• Network Encryption Software

Name

• GnuTLS

License

• open-source

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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