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LexborApplication

CVE-2026-29079

HIGH · 7.5 CVSS v3.1 Published 2026-03-13
Fix available
A fix is available. Upgrade to 2.7.0 or later.
See remediation →
84/100
Remediation priority · High
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
Lexbor is a web browser engine library. Prior to 2.7.0, a type‑confusion vulnerability exists in Lexbor’s HTML fragment parser. When ns = UNDEF, a comment is created using the “unknown element” constructor. The comment’s data are written into the element’s fields via an unsafe cast, corrupting the qualified_name field. That corrupted value is later used as a pointer and dereferenced near the zero page. This vulnerability is fixed in 2.7.0.

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

Type-confusion vulnerability in Lexbor's HTML fragment parser where, when ns equals UNDEF, a comment is incorrectly constructed using the 'unknown element' constructor. The comment's data is written into element fields via an unsafe cast, corrupting the qualified_name field which is then dereferenced as a pointer near the zero page, causing memory corruption.

MitigationUpgrade Lexbor library to version 2.7.0 or later. If immediate upgrading is not feasible, implement input validation or sandboxing around HTML fragment parsing to limit exposure to untrusted content.

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
LexborApplication
Affected:< 2.7.0

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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. Identify Lexbor library usage
    Search project dependencies (package.json, Cargo.toml, conanfile.txt, or library binaries) for 'lexbor' reference, or grep source code for '#include <lexbor>' or 'lexbor_' function calls
    Affected if Lexbor library is present in the codebase or dependencies
  2. Check installed Lexbor version
    Run 'lexbor --version' if CLI available, or inspect version header file (version.h) in Lexbor installation directory, or check the library version in package manager output
    Affected if Version is lower than 2.7.0 (e.g., 2.6.0, 2.5.0, etc.)
  3. Confirm HTML fragment parser is in use
    Search source code for calls to lxb_html_fragment_parse(), lxb_html_fragment_parse_cb(), or similar fragment parsing functions from Lexbor HTML module
    Affected if Code calls HTML fragment parsing functions from Lexbor
  4. Check for untrusted HTML input handling
    Review code paths that feed external/untrusted HTML content into Lexbor fragment parser; inspect data flow from HTTP requests, file uploads, or user inputs to lxb_html_fragment_parse* functions
    Affected if Fragment parser processes HTML from untrusted or external sources without prior sanitization
  5. Verify ns parameter usage in fragment parsing
    Inspect calls to lxb_html_fragment_parse() and related functions to see if ns (namespace) parameter is set to UNDEF or NULL, or if default namespace handling is in use
    Affected if Namespace parameter is not explicitly set to a valid value or defaults to UNDEF

User is affected if Lexbor library version is below 2.7.0 AND the application uses Lexbor's HTML fragment parser to process HTML content with namespace set to UNDEF or default.

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 2.7.0 or later
Fixed in 2.7.0
Interim mitigation

Upgrade Lexbor library to version 2.7.0 or later. If immediate upgrading is not feasible, implement input validation or sandboxing around HTML fragment parsing to limit exposure to untrusted content.

Recommended fix High confidence

Lexbor 2.7.0

  1. 1. Identify all projects and dependencies that use the vulnerable Lexbor library (version < 2.7.0)
  2. 2. Locate the Lexbor dependency in your project's dependency management system (e.g., package.json, conanfile.txt, CMakeLists.txt, or submodule)
  3. 3. Update the Lexbor version constraint to specify version 2.7.0 or higher
  4. 4. Run dependency resolution to fetch the new version (e.g., npm update, pip install -r requirements.txt, conan install, or git submodule update)
  5. 5. Rebuild any compiled components that link against Lexbor
  6. 6. Verify the upgrade by running your project's test suite
  7. 7. Deploy the updated application

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

Fix this in Lexbor Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2026-29079 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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