libexpat is a widely used XML library; this overflow can enable remote code execution or widespread DoS in many applications and infrastructures.
CVE-2026-102633
Integer overflow in libexpat enabling heap overflow leading to RCE/DoS on 32-bit systems.
Is CVE-2026-102633 being exploited?
Not confirmed. CVE-2026-102633 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.35% probability of exploitation in the next 30 days.
How severe is CVE-2026-102633?
CVE-2026-102633 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-102633?
Yes. A fix has been recorded for CVE-2026-102633. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-102633 affect?
CVE-2026-102633 affects libexpat 2.7.2 through 2.8.5 (32-bit builds), Any application or service statically/dynamically linking vulnerable libexpat (XML parsers, toolchains, servers). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-102633?
Upgrade to patched libexpat release/commit, rebuild dependent binaries, block untrusted XML inputs on 32-bit hosts.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Heap buffer overflow via crafted XML on 32-bit when parsing with libexpat 2.7.2–2.8.5; may cause memory corruption, DoS, or remote code execution.
Immediate action required
- affected>= 2.7.2 and <= 2.8.5
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.