CVE-2026-33846

Description

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.

How to fix CVE-2026-33846

To remediate CVE-2026-33846, upgrade the affected package to a fixed version below.

• —upgrade to 3.8.13-r0 or later
• —upgrade to 3.7.1-5+deb11u10 or later

Is CVE-2026-33846 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 3.8.13-r0
• from 0, < 3.7.1-5+deb11u10

CVSS scores

References (2)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2026-33846
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-33846