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.
Weakness
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.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat Enterprise Linux 10 | RedHat | gnutls-0:3.8.10-4.el10_2 | * |
| Red Hat Enterprise Linux 10.0 Extended Update Support | RedHat | gnutls-0:3.8.9-9.el10_0.19 | * |
| Red Hat Enterprise Linux 8 | RedHat | gnutls-0:3.6.16-8.el8_10.6 | * |
| Red Hat Enterprise Linux 8 | RedHat | gnutls-0:3.6.16-8.el8_10.6 | * |
| Red Hat Enterprise Linux 9 | RedHat | gnutls-0:3.8.10-4.el9_8 | * |
| Red Hat Enterprise Linux 9 | RedHat | gnutls-0:3.8.10-4.el9_8 | * |
| Red Hat Hardened Images | RedHat | gnutls-main-3.8.13-1.hum1 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/cds-rhel9:1781525684 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/haproxy-rhel9:1781525671 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/installer-rhel9:1781525693 | * |
| Red Hat Update Infrastructure 5 | RedHat | rhui5/rhua-rhel9:1781525739 | * |
| Gnutls28 | Ubuntu | devel | * |
| Gnutls28 | Ubuntu | esm-infra/xenial | * |
| Gnutls28 | Ubuntu | fips-preview/jammy | * |
| Gnutls28 | Ubuntu | fips-updates/jammy | * |
| Gnutls28 | Ubuntu | fips-updates/noble | * |
| Gnutls28 | Ubuntu | jammy | * |
| Gnutls28 | Ubuntu | noble | * |
| Gnutls28 | Ubuntu | questing | * |
| Gnutls28 | Ubuntu | resolute | * |
| Gnutls28 | Ubuntu | upstream | * |
Potential Mitigations
Related Attack Patterns
References
- https://access.redhat.com/errata/RHSA-2026:13274
- https://access.redhat.com/errata/RHSA-2026:20611
- https://access.redhat.com/errata/RHSA-2026:20612
- https://access.redhat.com/errata/RHSA-2026:20613
- https://access.redhat.com/errata/RHSA-2026:26319
- https://access.redhat.com/errata/RHSA-2026:26409
- https://access.redhat.com/security/cve/CVE-2026-33846
- https://bugzilla.redhat.com/show_bug.cgi?id=2450625