CVE-2026-56407 Integer overflow in libexpat

What is CVE-2026-56407?

CVE-2026-56407 is a medium-severity vulnerability in Libexpat Project Libexpat, published on 21 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textLen.

Weakness: CWE-190

Which versions are affected by CVE-2026-56407?

It affects 1 product.

Products include Libexpat Project Libexpat.

How do I fix CVE-2026-56407?

Upgrade to a fixed version.

Is CVE-2026-56407 being exploited?

There is no known exploitation of CVE-2026-56407 in the wild and no public exploit code.

Other vulnerabilities in Libexpat Project Libexpat

• CVE-2024-45490 Integer overflow in n/a Critical 9.8
• CVE-2026-66046 Expat Denial of Service via storeAtts() Quadratic Complexity High 8.7
• CVE-2021-46143 Integer overflow in n/a High 8.1
• CVE-2017-11742 Privilege escalation in n/a High 7.8
• CVE-2025-59375 Denial of service in libexpat High 7.5

All Libexpat Project Libexpat vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2026-56407, AZL-90237, BELL-CVE-2026-56407, CLSA-2026-1785945124, CLSA-2026-1786027135, CLSA-2026-1786029018 and 10 more.