No exploitation reportedFix available

CVE-2026-42009

No exploitation reported by the sources we read.

Published2026-05-18
WeaknessCWE-475

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2026-05-1813:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-42009?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-42009?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Redhat enterprise linux

Branch	Affected	Fixed in	Source
6.0	= 6.0	no fix published	NVD
7.0	= 7.0	no fix published	NVD
8.0	= 8.0	no fix published	NVD
9.0	= 9.0	no fix published	NVD
9.8	= 9.8	no fix published	NVD
10.0	= 10.0	no fix published	NVD
10.2	= 10.2	no fix published	NVD

Redhat enterprise linux for power little endian

Branch	Affected	Fixed in	Source
8.0	= 8.0_ppc64le	no fix published	NVD
9.0	= 9.0_ppc64le	no fix published	NVD
10.0	= 10.0	no fix published	NVD
10.2	= 10.2	no fix published	NVD

Redhat enterprise linux for els

Branch	Affected	Fixed in	Source
8.10	= 8.10	no fix published	NVD
9.8	= 9.8	no fix published	NVD
10.2	= 10.2	no fix published	NVD

11 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

gnutlsAlmaLinux:10all versions · fixed in 3.8.10-4.el10_2and 5 other packages
gnutlsAlmaLinux:9all versions · fixed in 3.8.10-4.el9_8and 4 other packages
gnutlsAlmaLinux:8all versions · fixed in 3.6.16-8.el8_10.6and 4 other packages

Vendor advisories

CVE-2026-42009 Red Hat Product Security902 products fixed
gnutls: gnutls: Denial of Service via DTLS packet reordering vulnerability
RHSA-2026:82888 Red Hat Product Security1 product fixed
Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.17.2
RHSA-2026:82857 Red Hat Product Security1 product fixed
Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2
RHSA-2026:82372 Red Hat Product Security4 products fixed
Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2
RHSA-2026:82354 Red Hat Product Security4 products fixed
Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2
RHSA-2026:82347 Red Hat Product Security8 products fixed
Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

33 more advisories

Full record on NVD

Fix

Vendor fix Red Hat Product Security RHSA-2026:82888 · 1 productBefore applying this update, make sure all previously released errata relevant to your system have been applied. The steps to apply the upgraded images are different depending on the installation plan approval policy you used when installing the cert-manager Operator for Red Hat OpenShift. - If t…
Vendor fix Red Hat Product Security RHSA-2026:74674 · 1 productFor more information visit https://access.redhat.com/errata/RHSA-2026:74674
Vendor fix Red Hat Product Security RHSA-2026:65839 · 1 productFor OpenShift Container Platform 4.13 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.redhat.com/en/documentation/openshift_container_platform/4.…
Vendor fix Red Hat Product Security RHSA-2026:59831 · 1 productFor OpenShift Container Platform 4.12 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.redhat.com/en/documentation/openshift_container_platform/4.…
Vendor fix Red Hat Product Security RHSA-2026:60019 · 4 productsFor OpenShift Container Platform 4.17 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.redhat.com/en/documentation/openshift_container_platform/4.…
Vendor fix Red Hat Product Security RHSA-2026:56853 · 4 productsFor OpenShift Container Platform 4.16 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.redhat.com/en/documentation/openshift_container_platform/4.…

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-05-18
OpenCVESSVC decisionnone—
CNACVSS 3.17.5read 2026-10-23
CNAweakness (CWE)CWE-475read 2026-10-23
FIRST EPSSEPSS score1.1 %2026-10-23
OSVaffected packages—
Microsoft MSRCadvisory—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2026-05-18
Last Modified: 2026-10-14
NVD status: Modified
MSRC Title: Gnutls: gnutls: denial of service via dtls packet reordering vulnerability

Frequently asked questions

What is CVE-2026-42009?

Is CVE-2026-42009 actively exploited?

Active exploitation of CVE-2026-42009 has not been confirmed. Its EPSS score was 1.1% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-42009?

CVE-2026-42009 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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