CVE catalog

CVE-2026-66046

Severity: High · CVSS 8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published: Aug 10, 2026, 4:16:50 AM UTC
Updated: Aug 18, 2026, 3:16:57 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.74% · Oct 22, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	expat	sid	`2.9.0-1`	fixed
Debian	expat	forky	`2.9.0-1`	fixed
Debian	expat	trixie	`2.8.3-1~deb13u1`	vulnerable
Debian	expat	trixie-security	`2.9.0-1~deb13u1`	fixed
Debian	expat	bookworm	`2.5.0-1+deb12u2`	vulnerable
Debian	expat	bookworm-security	`2.5.0-1+deb12u5`	fixed
Cpe	libexpat	Not reported	Not reported	unknown
Ubuntu	expat	noble	`2.6.1-2ubuntu0.6`	fixed
Ubuntu	libexpat1	noble	`2.6.1-2ubuntu0.6`	fixed
Ubuntu	libexpat1-dev	noble	`2.6.1-2ubuntu0.6`	fixed
Alpine	expat	3.21	`2.8.4-r0`	fixed
Alpine	expat	3.22	`2.8.4-r0`	fixed
Alpine	expat	3.23	`2.8.4-r0`	fixed
Alpine	expat	3.24	`2.8.4-r0`	fixed
Opensuse	expat	tumbleweed	`2.8.4-1.1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	expat	source	sid	`2.8.4-1`	not yet assigned	Not reported	[1144925]
Debian	expat	source	forky	`2.8.4-1`	not yet assigned	Not reported	[1144925]
Debian	expat	source	trixie	`2.9.0-1~deb13u1`	not yet assigned	Not reported	[1144925]
Debian	expat	source	bookworm	`2.5.0-1+deb12u4`	not yet assigned	Not reported	[1144925]
Ubuntu	expat	deb	noble	`2.6.1-2ubuntu0.6`	Not reported	Not reported	Not reported
Ubuntu	libexpat1	deb	noble	`2.6.1-2ubuntu0.6`	Not reported	Not reported	Not reported
Ubuntu	libexpat1-dev	deb	noble	`2.6.1-2ubuntu0.6`	Not reported	Not reported	Not reported
Alpine	expat	apk	3.21	`2.8.4-r0`	Not reported	ALPINE-CVE-2026-66046	Not reported
Alpine	expat	apk	3.22	`2.8.4-r0`	Not reported	ALPINE-CVE-2026-66046	Not reported
Alpine	expat	apk	3.23	`2.8.4-r0`	Not reported	ALPINE-CVE-2026-66046	Not reported
Alpine	expat	apk	3.24	`2.8.4-r0`	Not reported	ALPINE-CVE-2026-66046	Not reported
Opensuse	expat	rpm	tumbleweed	`2.8.4-1.1`	Not reported	OPENSUSE-SU-2026:11733-1	Not reported

[Debian bug #1144925]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[expat]Unknown
Details (4)
- 2.5.0-1+deb12u2 · amd64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u2 · arm64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · amd64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · arm64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
[libexpat1]Unknown
Source package: [expat]
Details (4)
- 2.5.0-1+deb12u2 · amd64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u2 · arm64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · amd64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · arm64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
[libexpat1-dev]Unknown
Source package: [expat]
Details (4)
- 2.5.0-1+deb12u2 · amd64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u2 · arm64 · bookworm
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · amd64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm
- 2.5.0-1+deb12u3 · arm64 · bookworm-security
  Affected · Fixed: 2.5.0-1+deb12u4
  nvd · expat · debian · bookworm

[openSUSE Tumbleweed]

[expat]Unknown
Source package: [expat]
Details (1)
- 2.8.2-1.1 · x86_64 · tumbleweed
  Affected · Fixed: 2.8.4-1.1
  nvd · expat · opensuse · tumbleweed
[libexpat1]Unknown
Source package: [expat]
Details (1)
- 2.8.2-1.1 · x86_64 · tumbleweed
  Unknown · Fixed: 2.8.4-1.1
  Version impact unknown
  nvd · expat · opensuse · tumbleweed
[libexpat1-32bit]Unknown
Source package: [expat]
Details (1)
- 2.8.2-1.1 · x86_64 · tumbleweed
  Unknown · Fixed: 2.8.4-1.1
  Version impact unknown
  nvd · expat · opensuse · tumbleweed
[libexpat-devel]Unknown
Source package: [expat]
Details (1)
- 2.8.2-1.1 · x86_64 · tumbleweed
  Unknown · Fixed: 2.8.4-1.1
  Version impact unknown
  nvd · expat · opensuse · tumbleweed
[libexpat-devel-32bit]Unknown
Source package: [expat]
Details (1)
- 2.8.2-1.1 · x86_64 · tumbleweed
  Unknown · Fixed: 2.8.4-1.1
  Version impact unknown
  nvd · expat · opensuse · tumbleweed

Observed: Oct 23, 2026, 9:42:28 PM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]