NVD / CVE Program· CNA canonical

CVE-2026-6653: libxml2: Use after free in xmlParseInternalSubset via improper entity resolution handling

Noroxi assessment

Priority: Monitor (action score 28/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.35% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
Fixed version: GNOME libxml2 2.11.0.

Low priority for now. Upgrade to GNOME libxml2 2.11.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.0 · v4.0—No exploit Fix available

Published: Jun 22, 2026
Updated: Oct 25, 2026
EPSS: 0.3% · 28th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 28 / 40 · 7.0 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.3%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · canonical: 7.0; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
xmlsoft	libxml2	cpe:2.3:a:xmlsoft:libxml2

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

xmlsoft libxml22.9.11 and later · up to 2.11.0 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (canonical). Independent of NVD's CPE analysis and usually ahead of it.

GNOME libxml2
- 2.9.11 and later · before 2.11.0affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
AlmaLinux:8	libxml2	before 2.9.7-21.el8_10.8	2.9.7-21.el8_10.8
AlmaLinux:8	libxml2-devel	before 2.9.7-21.el8_10.8	2.9.7-21.el8_10.8
AlmaLinux:8	python3-libxml2	before 2.9.7-21.el8_10.8	2.9.7-21.el8_10.8
AlmaLinux:9	libxml2	before 2.9.13-14.el9_8.4	2.9.13-14.el9_8.4
AlmaLinux:9	libxml2-devel	before 2.9.13-14.el9_8.4	2.9.13-14.el9_8.4
AlmaLinux:9	python3-libxml2	before 2.9.13-14.el9_8.4	2.9.13-14.el9_8.4
Debian:12	libxml2	from 0	—
Debian:14	libxml2	before 2.14.5+dfsg-0.1	2.14.5+dfsg-0.1
Red Hat:enterprise_linux:8::appstream	libxml2-debuginfo	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:8::appstream	libxml2-debugsource	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:8::appstream	libxml2-devel	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:8::appstream	python3-libxml2-debuginfo	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:8::baseos	libxml2	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:8::baseos	python3-libxml2	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Red Hat:enterprise_linux:9::appstream	libxml2-debuginfo	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Red Hat:enterprise_linux:9::appstream	libxml2-debugsource	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Red Hat:enterprise_linux:9::appstream	libxml2-devel	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Red Hat:enterprise_linux:9::appstream	python3-libxml2-debuginfo	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Red Hat:enterprise_linux:9::baseos	libxml2	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Red Hat:enterprise_linux:9::baseos	python3-libxml2	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4
Rocky Linux:8	libxml2	before 0:2.9.7-21.el8_10.8	0:2.9.7-21.el8_10.8
Rocky Linux:9	libxml2	before 0:2.9.13-14.el9_8.4	0:2.9.13-14.el9_8.4

Same product

xmlsoft: all records

Other highest-scoring records for the same primary product.

CVE-2008-3529Heap-based buffer overflow in the xmlParseAttValueComplex function in parser.c in libxml2 before 2.7.0 allows context-dependent attackers to
47Plan
CVE-2017-7376Buffer overflow in libxml2 allows remote attackers to execute arbitrary code by leveraging an incorrect limit for port values when handling
46Plan
CVE-2022-40303An issue was discovered in libxml2 before 2.10.3.
42Plan

Published before and after this one in the same product

← EarlierCVE-2026-0989Jan 15, 2026 · Libxml2: unbounded relaxng include recursion leading to stack overflow
14Monitor
← EarlierCVE-2026-6732Apr 23, 2026 · Libxml2: libxml2: denial of service via crafted xsd-validated document
30Monitor
Later →CVE-2026-11979Jun 29, 2026 · Stack-Based Buffer Overflow in libxml2
7Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
GNOME libxml2	2.11.0	Vendor (CNA)
almalinux:libxml2	2.9.13-14.el9_8.4 · AlmaLinux:9	Package registry (OSV)
almalinux:libxml2-devel	2.9.13-14.el9_8.4 · AlmaLinux:9	Package registry (OSV)
almalinux:python3-libxml2	2.9.13-14.el9_8.4 · AlmaLinux:9	Package registry (OSV)
debian:libxml2	2.14.5+dfsg-0.1 · Debian:14	Package registry (OSV)
red hat:libxml2	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::baseos	Package registry (OSV)
red hat:libxml2-debuginfo	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
red hat:libxml2-debugsource	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
red hat:libxml2-devel	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
red hat:python3-libxml2	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::baseos	Package registry (OSV)
red hat:python3-libxml2-debuginfo	0:2.9.13-14.el9_8.4 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
rocky linux:libxml2	0:2.9.13-14.el9_8.4 · Rocky Linux:9	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Geoffrey Humphreysfinder

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2024-56171489 days apartlibxml2 before 2.12.10 and 2.13.x before 2.13.6 has a use-after-free in xmlSchemaIDCFillNodeTables and xmlSchemaBubbleIDCNodeTables in xmlsc
39Monitor
CVE-2022-49043512 days apartxmlXIncludeAddNode in xinclude.c in libxml2 before 2.11.0 has a use-after-free.
31Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:08 PM UTC

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