CVE-2026-76641 Expat Out-of-Bounds Read via dtdCopy
Attackers can trigger memory corruption and denial of service in libexpat by processing malicious XML with external entity parsers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-76641?
CVE-2026-76641 is a high-severity memory corruption vulnerability in libexpat, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.
Weakness: CWE-125
Which versions are affected by CVE-2026-76641?
How do I fix CVE-2026-76641?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-76641 being exploited?
There is no known exploitation of CVE-2026-76641 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-76641, AZL-96932, BELL-CVE-2026-76641, CLSA-2026-1791324825, CLSA-2026-1791325909, CLSA-2026-1791326154 and 3 more.