dbcve.org
CWE-407Weakness · CWE-407

CVE-2026-66046

HIGH · 7.5 CVSS v3.1 Published 2026-08-18
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click Patch available 3 days old

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
Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

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

A detailed technical summary for this CVE is being prepared.

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

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
Patch available Apply the vendor patch
Vendor patch github.com →
Recommended fix Moderate confidence

Expat 2.8.4 or later (check https://github.com/libexpat/libexpat/releases for the latest stable release)

  1. 1. Identify all applications and systems using the Expat XML parsing library (libexpat).
  2. 2. Check the currently installed version of Expat by running 'expat --version' or checking the library file version.
  3. 3. Visit the official Expat repository at https://github.com/libexpat/libexpat/releases to identify the latest stable release.
  4. 4. Download the latest version of Expat (version 2.8.4 or later, as 2.8.3 is mentioned as the affected version).
  5. 5. For systems using Expat as a system library: update the library package via the system's package manager (e.g., apt-get update && apt-get install libexpat1-dev on Debian/Ubuntu, or yum update expat on RHEL/CentOS).
  6. 6. For applications bundling Expat: rebuild the application with the updated Expat source code.
  7. 7. Restart any services or applications that use the Expat library to ensure the new version is loaded.
  8. 8. Test XML parsing functionality to ensure the update does not break existing functionality.
Caveat Minor: Upgrading Expat is generally safe; however, test applications that rely on specific parsing behaviors as minor behavior changes may occur between versions.

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

We can apply and verify the patch for your build — typical engagement from $3,900. Get the patch applied

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-66046 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-66046 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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