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Vulnerabilities

Vulnerability · CVE-2026-66046

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 at

Published Aug 18, 2026 · catalog updated Oct 16, 2026 · Expat through 2.8.3 contains

Check if you run it

No confirmed exploitation is on record for CVE-2026-66046. EPSS is 0.74%. Act only if a listed version of Expat through 2.8.3 contains is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Expat through 2.8.3 contains).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.74%
Remediation
Advisory link
Affected products
Debian:12 expat · Debian:13 expat · Debian:14 expat

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Debian:12 expat0 → 2.5.0-1+deb12u4
  • Debian:13 expat0 → 2.9.0-1~deb13u1
  • Debian:14 expat0 → 2.8.4-1

How to fix CVE-2026-66046

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-66046. EPSS is 0.74%. Act only if a listed version of Expat through 2.8.3 contains is installed.

Which versions are affected?

Compare what you have installed with 0 → 2.5.0-1+deb12u4, 0 → 2.9.0-1~deb13u1, 0 → 2.8.4-1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.74%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Debian security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 18, 2026 · OpenSSF OSV / OSV Scanner

    Detected

    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

  2. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    expat fixed in 2.5.0-1+deb12u4; expat fixed in 2.9.0-1~deb13u1; expat fixed in 2.8.4-1

  3. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    expat fixed in 2.5.0-1+deb12u4

  4. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    expat fixed in 2.9.0-1~deb13u1

  5. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    expat fixed in 2.8.4-1

  6. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.