CVE-2026-56407: libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textLen.
CSIRTS triage
- What
- An integer overflow in doProlog is related to storeEntityValue and entity textLen.
- Who is affected
- Users of libexpat versions before 2.8.2 are affected.
- Urgency
- Remediation is medium urgency due to the medium severity rating.
- Action
- Upgrade to libexpat version 2.8.2 or later.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56407
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-564070.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-56407 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- medium[UPDATE] [medium] libexpat: Multiple vulnerabilities allow unspecified attackcert-bund
- unknownDSA-6404-1 expat - security updatedebian
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