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Vulnerability · Published Aug 20, 2026 · Assigned by mitre

CVE-2026-76957

Medium 4.9

In plain English

A medium-severity use-after-free in libexpat from libexpat project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 1% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.9Medium
Exploit odds (30 days)0.1%top 98.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after-free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21expat2.8.4-r0ALPINE-CVE-2026-76957
Alpine:v3.22expat2.8.4-r0ALPINE-CVE-2026-76957
Alpine:v3.23expat2.8.4-r0ALPINE-CVE-2026-76957
Alpine:v3.24expat2.8.4-r0ALPINE-CVE-2026-76957
Debian:12expat2.5.0-1+deb12u3DEBIAN-CVE-2026-76957
Debian:13expat2.9.0-1~deb13u1DEBIAN-CVE-2026-76957
Debian:14expat2.8.4-1DEBIAN-CVE-2026-76957
Ubuntu:22.04:LTScadaverno fix listedUBUNTU-CVE-2026-76957
Ubuntu:24.04:LTScadaverno fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.04:LTScadaverno fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10cadaverno fix listedUBUNTU-CVE-2026-76957
Ubuntu:22.04:LTSexpat2.4.7-1ubuntu0.9USN-8813-1
Ubuntu:22.04:LTSexpat2.4.7-1ubuntu0.9UBUNTU-CVE-2026-76957
Ubuntu:24.04:LTSexpat2.6.1-2ubuntu0.6UBUNTU-CVE-2026-76957
Ubuntu:24.04:LTSexpat2.6.1-2ubuntu0.6USN-8813-1
Ubuntu:26.04:LTSexpat2.7.4-1ubuntu0.2USN-8813-1
Ubuntu:26.04:LTSexpat2.7.4-1ubuntu0.2UBUNTU-CVE-2026-76957
Ubuntu:22.04:LTSinsighttoolkit4no fix listedUBUNTU-CVE-2026-76957
Ubuntu:22.04:LTSmatanzano fix listedUBUNTU-CVE-2026-76957
Ubuntu:24.04:LTSmatanzano fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.04:LTSmatanzano fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10matanzano fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10swish-eno fix listedUBUNTU-CVE-2026-76957
Ubuntu:22.04:LTStdomno fix listedUBUNTU-CVE-2026-76957
Ubuntu:24.04:LTStdomno fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.04:LTStdomno fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10tdomno fix listedUBUNTU-CVE-2026-76957
Ubuntu:22.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-76957
Ubuntu:24.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10wbxml2no fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.04:LTSxmlrpc-cno fix listedUBUNTU-CVE-2026-76957
Ubuntu:26.10xmlrpc-cno fix listedUBUNTU-CVE-2026-76957

Affected products (as reported)

VendorProductVersions
libexpat project libexpat 0 – before 2.8.4

Weakness: CWE-416 · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

References