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VulnerabilityPublished Updated

CVE-2026-42009: gnutls · Undefined Behavior for Input to API

Affects gnutlsSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.8.13 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.

Sources agree

CVSS scores by source
CNA (redhat)CVSS 3.17.5
ADP (redhat-SADP)CVSS 3.17.5
EPSS
1.3% chance of exploitation in 30 days – higher than 71% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.8.13
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 18 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade gnutls to 3.8.13.

Affected software

ProductAffectedFixed in
gnutlsAffected
  • <3.8.13
Fixed in
  • 3.8.13

AI-suggested

Red Hat has issued security advisories and updates addressing this vulnerability in GnuTLS packages, notably for Red Hat Enterprise Linux 8. The advisories recommend applying the updated GnuTLS RPM packages to remediate the issue. For Red Hat Enterprise Linux 10, patch status is not explicitly confirmed in the provided data; therefore, users should monitor the official Red Hat advisory page (https://access.redhat.com/security/cve/CVE-2026-42009) for updates and apply any available fixes promptly. If you cannot patch yet, consider limiting exposure of DTLS services to untrusted networks if feasible.

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.

References

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