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7.5High

Gnu Gnutls

CVE-2026-42009

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.

What this means for your business

  • It affects Gnutls. It matters if your company, or a supplier that handles your data, runs it.
  • An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 1% chance of attack attempts being seen in the next 30 days, ranking above 69% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Gnutls, and which version. The affected versions are listed further down this page.
  2. 2If you do, follow the vendor's guidance. No patch reference has been published yet.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Check if you’re exposedBook a call

Scoring

CVSS
7.5 (v3.1)
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-475
Assigned by
secalert@redhat.com

Dates

Published
2026-05-18
Last modified
2026-09-18
Sources
NVD

Affected products

  • Gnu Gnutlsall versions
  • Redhat Hardened Imagesall versions
  • Redhat Openshift Container Platform4.0
  • Redhat Enterprise Linux6.0, 7.0, 8.0, 9.0, 9.8, 10.0, 10.2
  • Redhat Enterprise Linux For Els8.10, 9.8, 10.2
  • Redhat Enterprise Linux For Ibm Z Systems8.0 s390x, 9.0 s390x, 10.2
  • Redhat Enterprise Linux For Ibm Z Systems Els8.10, 9.8, 10.2
  • Redhat Enterprise Linux For Power Little Endian8.0 ppc64le, 9.0 ppc64le, 10.0, 10.2
  • Redhat Enterprise Linux For Power Little Endian Els8.10, 9.8, 10.2
  • Redhat Enterprise Linux For Eus9.8, 10.2
  • Redhat Enterprise Linux For Ibm Z Systems Eus9.8, 10.2
  • Redhat Enterprise Linux For Power Little Endian Eus9.8, 10.2

As listed in the NVD configuration data. Not a statement about your estate.

References