CVE-2026-33846: Gnutls: gnutls: denial of service via heap buffer overflow in dtls handshake fragment reassembly

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-04 · updated 2026-10-26
Weakness: CWE-130

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.

Affected products

Red Hat Cert Manager support for Red Hat OpenShift release 1.17: all versions — fixed in 1791371069, 1791371080, 1791788287, 1791970484
Red Hat Cert Manager support for Red Hat OpenShift release 1.18: all versions — fixed in 1789029076, 1791459707, 1791459711, 1791459759, 1791966259
Red Hat Cert Manager support for Red Hat OpenShift release 1.20: all versions — fixed in 1790598593
Red Hat OpenShift Container Platform 4.18: all versions — fixed in 418.94.202608142238-0
Red Hat AI Inference Server 3.2: all versions — fixed in 1782951012, 1782951051, 1782951244
Red Hat Discovery 2: all versions — fixed in 1782159791, 1782166952
Red Hat Enterprise Linux 10: all versions — fixed in 0:3.8.10-4.el10_2
Red Hat Enterprise Linux 10.0 Extended Update Support: all versions — fixed in 0:3.8.9-9.el10_0.19
Red Hat Enterprise Linux 7 Extended Lifecycle Support: all versions — fixed in 0:3.3.29-9.el7_9.1
Red Hat Enterprise Linux 8: all versions — fixed in 0:3.6.16-8.el8_10.6
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support: all versions — fixed in 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On: all versions — fixed in 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support: all versions — fixed in 0:3.6.16-5.el8_6.5, 0:4.13-3.el8_6.2
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On: all versions — fixed in 0:3.6.16-5.el8_6.5, 0:4.13-3.el8_6.2
Red Hat Enterprise Linux 8.8 Telecommunications Update Service: all versions — fixed in 0:3.6.16-7.el8_8.4, 0:4.13-4.el8_8.1
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions: all versions — fixed in 0:3.6.16-7.el8_8.4, 0:4.13-4.el8_8.1
Red Hat Enterprise Linux 9: all versions — fixed in 0:3.8.10-4.el9_8
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions: all versions — fixed in 0:3.7.6-21.el9_2.7
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions: all versions — fixed in 0:3.8.3-4.el9_4.6
Red Hat Enterprise Linux 9.6 Extended Update Support: all versions — fixed in 0:3.8.3-6.el9_6.4
Red Hat Hardened Images: all versions — fixed in 3.8.13-1.hum1
Red Hat OpenShift AI 3.4: all versions — fixed in 1790703542
Red Hat OpenShift Container Platform 4.12: all versions — fixed in 412.86.202608241157-0
Red Hat OpenShift Container Platform 4.13: all versions — fixed in 413.92.202609080414-0
Red Hat OpenShift Container Platform 4.14: all versions — fixed in 414.92.202608172040-0
Red Hat OpenShift Container Platform 4.15: all versions — fixed in 415.92.202608180329-0
Red Hat OpenShift Container Platform 4.16: all versions — fixed in 416.94.202608150307-0
Red Hat OpenShift Container Platform 4.17: all versions — fixed in 417.94.202608250221-0
Red Hat OpenShift Container Platform 4.19: all versions — fixed in 4.19.9.6.202608182320-0
Red Hat Update Infrastructure 5: all versions — fixed in 1781525671, 1781525684, 1781525693, 1781525739, 1787135742, 1787241211

How to fix

Upgrade to a fixed version: Red Hat Cert Manager support for Red Hat OpenShift release 1.17 1791371069, 1791371080, 1791788287, 1791970484; Red Hat Cert Manager support for Red Hat OpenShift release 1.18 1789029076, 1791459707, 1791459711, 1791459759; Red Hat Cert Manager support for Red Hat OpenShift release 1.20 1790598593; Red Hat OpenShift Container Platform 4.18 418.94.202608142238-0; Red Hat AI Inference Server 3.2 1782951012, 1782951051, 1782951244; Red Hat Discovery 2 1782159791, 1782166952; Red Hat Enterprise Linux 10 0:3.8.10-4.el10_2; Red Hat Enterprise Linux 10.0 Extended Update Support 0:3.8.9-9.el10_0.19; Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:3.3.29-9.el7_9.1; Red Hat Enterprise Linux 8 0:3.6.16-8.el8_10.6; Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1; Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1. Check the vendor advisory for mitigations.

References

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