CVE-2026-42009: Gnutls: gnutls: denial of service via dtls packet reordering vulnerability

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: 2026-05-18 · updated 2026-10-30
Weakness: CWE-475

Description

A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.

Affected products

[UNKNOWN] gnutls: all versions
Red Hat Enterprise Linux: 6.0, 7.0, 8.0, 9.0, 9.8, 10.0 (+1) (and their updates)
RedHat Enterprise Linux For Els: 8.10, 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Eus: 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Ibm Z Systems: 8.0_s390x, 9.0_s390x, 10.2 (and their updates)
RedHat Enterprise Linux For Ibm Z Systems Els: 8.10, 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Ibm Z Systems Eus: 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Power Little Endian: 8.0_ppc64le, 9.0_ppc64le, 10.0, 10.2 (and their updates)
RedHat Enterprise Linux For Power Little Endian Els: 8.10, 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Power Little Endian Eus: 9.8, 10.2 (and their updates)
RedHat Enterprise Linux For Update Services For Sap Solutions: 9.8 (and their updates)
RedHat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions: 9.8 (and their updates)
RedHat Hardened Images: all versions
Red Hat OpenShift Container Platform 4.18: 4.0 (and their updates)
[UNKNOWN] gnutls: before 3.8.13 — fixed in 3.8.13
Red Hat Cert Manager support for Red Hat OpenShift release 1.17: all versions — fixed in 1791371080
Red Hat Cert Manager support for Red Hat OpenShift release 1.18: all versions — fixed in 1791459707
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 1782951051
Red Hat Discovery 2: all versions — fixed in 1782159791
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
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
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support: all versions — fixed in 0:3.6.16-5.el8_6.5
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
Red Hat Enterprise Linux 8.8 Telecommunications Update Service: all versions — fixed in 0:3.6.16-7.el8_8.4

How to fix

Upgrade to a fixed version: [UNKNOWN] gnutls 3.8.13; Red Hat Cert Manager support for Red Hat OpenShift release 1.17 1791371080; Red Hat Cert Manager support for Red Hat OpenShift release 1.18 1791459707; 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 1782951051; Red Hat Discovery 2 1782159791; 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. Check the vendor advisory for mitigations.

References

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