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Libxml2Framework / library · Xmlsoft

CVE-2026-6653

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-22
Fix available
A fix is available. Upgrade to after 2.11.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A Use After Free vulnerability exists in libxml2's xmlParseInternalSubset function in versions 2.9.11 through 2.11.0. The vulnerability stems from improper handling during entity resolution processing, allowing a remote attacker to trigger the UAF condition via specially crafted malicious XML input, resulting in denial of service.

MitigationUpdate libxml2 to version 2.11.1 or later. For applications using vulnerable libxml2 versions, rebuild and redeploy with the patched library to address the entity resolution handling flaw in xmlParseInternalSubset.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Libxml2Framework / library
Affected:>= 2.9.11, <= 2.11.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed libxml2 version
    Run `xml2-config --version` on the system, or check the library file version using `dpkg -l libxml2` (Debian/Ubuntu), `rpm -q libxml2` (RHEL/CentOS), or inspect the shared object file with `strings /usr/lib/libxml2.so.2 | grep '^2\.' | head -1`. In code, call xmlParserVersion() or link against libxml2 and print LIBXML_DOTTED_VERSION.
    Affected if The installed version falls between 2.9.11 and 2.11.0 inclusive (for example, 2.9.14, 2.10.3, or 2.11.0).
  2. Identify processes or applications using libxml2
    Run `ldd <application_binary>` to see if it links against libxml2, or use `lsof | grep libxml` to list processes with open libxml2 library handles. Check application dependency lists or container manifests for libxml2 packages.
    Affected if Any actively running application or service links to and uses the affected libxml2 library version.
  3. Verify XML parsing code paths
    Review application source code for calls to xmlReadFile, xmlParseDoc, xmlReadMemory, or similar libxml2 parsing functions. Search for usage of xmlParseInternalSubset indirectly through XML DTD/internal subset parsing. Use dynamic tracing with `strace -e trace=xml* <program>` or `ltrace` to observe libxml2 calls at runtime.
    Affected if The application parses untrusted or external XML documents using libxml2 functions, particularly those involving DTD internal subset or entity resolution.
  4. Inspect XML input sources
    Examine log files, upload directories, API endpoints, or configuration files that accept XML input. Check whether external entity (XXE) processing or DTD inclusion is enabled (look for XML_PARSE_DTDLOAD, XML_PARSE_DTDATTR, or XML_PARSE_NOENT flags in code or documentation).
    Affected if The environment processes XML from untrusted sources without input validation, or has DTD/external entity processing enabled.

You are affected if the installed libxml2 version is between 2.9.11 and 2.11.0 inclusive AND any application or service in your environment links to this library while parsing XML from potentially untrusted sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 2.11.0
Interim mitigation

Update libxml2 to version 2.11.1 or later. For applications using vulnerable libxml2 versions, rebuild and redeploy with the patched library to address the entity resolution handling flaw in xmlParseInternalSubset.

Recommended fix Moderate confidence

libxml2 2.11.1 or later

  1. 1. Identify all applications and systems that depend on libxml2
  2. 2. Check current installed version of libxml2 on each system (e.g., `xml2 --version` or check package manager)
  3. 3. Consult your Linux distribution or system's package manager for available patched packages
  4. 4. For source builds, download libxml2 version 2.11.1 or later from https://gitlab.gnome.org/GNOME/libxml2/-/releases
  5. 5. Test the upgrade in a staging environment before deploying to production
  6. 6. Apply the upgrade using your system's package manager or rebuild dependent applications against the new library version
  7. 7. Verify the fix by confirming the new libxml2 version is loaded and the vulnerability is resolved
Caveat Minor: Ensure any custom XML parsing code is compatible with the latest release; most applications will not be affected

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Libxml2 Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing24.0 h
  • Review / QA12.0 h
60.0 hours of engineering $10,240
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-6653 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data