How severe is CVE-2026-6653?

No CVSS score has been assigned to CVE-2026-6653 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-6653?

Affected package information for CVE-2026-6653 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-6653?

Upgrade the affected component to the fixed release for CVE-2026-6653, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

How do I detect CVE-2026-6653 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2026-6653 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is CVE-2026-6653 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-6653 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-6653?

CVE-2026-6653 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 27th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-6653?

CVE-2026-6653 is classified as Use After Free (CWE-416), XML External Entity (XXE) (CWE-611). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-6653 published, and has it been updated?

CVE-2026-6653 was published on June 22, 2026 and was last updated on September 22, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

Not in CISA KEV

CVE-2026-6653 — libxml2

CVE-2026-6653 is a Use After Free vulnerability. A fix is available — see the affected versions and patch details below.

libxml2: Use after free in xmlParseInternalSubset via improper entity resolution handling

Published

Jun 22, 2026

Updated

Sep 22, 2026

Affected

1 product

Patched

See advisory

Exploits

None indexed

Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-6653.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Description

Use After Free in libxml2's xmlParseInternalSubset from GNOME libxml2 version 2.9.11 to 2.11.0 allows a remote attacker to cause a denial-of-service via maliciously crafted XML input with improper entity resolution handling.

Affected Products

1 product · 1 configurations

Application

libxml2xmlsoft

≥ 2.9.11 && ≤ 2.11.0

range

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-6653, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This Moderate impact use-after-free vulnerability in libxml2 can lead to a denial of service in Red Hat products that process untrusted XML input. In the worst-case scenario, a remote attacker is able to provide specially crafted XML, which, if parsed by an affected application, could cause the application to crash.

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Updating to a fixed version of libxml2 (2.11.0 or later upstream, or a future RHEL errata) will fully resolve this issue.

Source: Red Hat security advisory for CVE-2026-6653 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Enterprise Linux 8	`libxml2-0:2.9.7-21.el8_10.8`	RHSA-2026:69655
Red Hat Enterprise Linux 9	`libxml2-0:2.9.13-14.el9_8.4`	RHSA-2026:61247
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/jetstack-cert-manager-rhel9:1790223279`	RHSA-2026:72394
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/cert-manager-istio-csr-rhel9:1790223719`	RHSA-2026:72395
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/cert-manager-operator-rhel9:1790272426`	RHSA-2026:72399
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/jetstack-cert-manager-acmesolver-rhel9:1790589998`	RHSA-2026:72470
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/cert-manager-istio-csr-rhel9:1790589914`	RHSA-2026:72475
Cert Manager support for Red Hat OpenShift release 1.20	`cert-manager/cert-manager-operator-rhel9:1790589855`	RHSA-2026:72476

UbuntuCRITICAL

USN-8456-1Ubuntu

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