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  4. CVE 2026 66046 expat denial of service via storeatts quadratic
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Back to active CVEs
High · CVSS 8.7CVE-2026-66046

Expat Denial of Service via storeAtts() Quadratic Complexity

Answer in brief

CVE-2026-66046 records a High severity (CVSS 8.7) vulnerability in Expat Denial of Service via storeAtts() Quadratic Complexity. The current sources do not mark it as known exploited. The current feed maps libexpat project/libexpat (generic), libexpat project/libexpat (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 18, 2026Updated Oct 1, 2026Source checked Oct 2, 2026First seen by HOL Aug 18, 2026Material review Oct 1, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.7
Exploitation
Not marked as known exploited
Affected software
3 mapped packages or products
Fix availability
Not reported

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps libexpat project/libexpat (generic), libexpat project/libexpat (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
ProductAffected versionsFixed versions
cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*Not reportedNot reported
Mapped affected packages and fixed versions
PackageAffected rangeFixed version
libexpat project/libexpatgeneric*Not reported
libexpat project/libexpatgeneric0Not reported

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for libexpat project/libexpat, libexpat project/libexpat.
  2. 2Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

  1. Published upstream

    Aug 18, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 1, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Aug 18, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • Source referencevulncheck.com
Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

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  • Weaver e-Bridge Unauthenticated Arbitrary File Read via saveYZJFileSame generic ecosystem
  • H3C CVM Unauthenticated File Upload via fileUpload/upload TokenSame generic ecosystem
  • LimeSurvey Community Edition 7.4.0 - Stored XSS through the Date/Time date_min question attributeSame generic ecosystem
  • Apache Traffic Server: SNI to Host header matching policy is not properly enforcedSame generic ecosystem
  • @orpc/json-schema: Prototype injection in smart coercionSame generic ecosystem

Record context

Vulnerability class
Missing Auth
EPSS
Not reported
CWE IDs
CWE-407
Source
CVE List V5
Source checked
Oct 2, 2026
References
2 linked sources
Open source record