CVE-2026-56412: libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.
CSIRTS triage
- What
- libexpat lacks handler call depth tracking, leading to a use-after-free condition.
- Who is affected
- Applications using libexpat versions before 2.8.2.
- Urgency
- Remediation is medium urgency as the severity is moderate and no exploitation has been reported.
- 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-2026-56412
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-2026-564120.10% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 1% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-56412 | coverage & exploitation status | NVD · CVE.org |
Recent advisories for libexpat
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- mediumCVE-2026-56409: xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputD…msrc · 2026-06-09
- mediumCVE-2026-56406: libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check tha…msrc · 2026-06-09
- mediumCVE-2026-56405: libexpat before 2.8.2 has an integer overflow in getAttributeId.msrc · 2026-06-09
- mediumCVE-2026-56411: xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION declarat…msrc · 2026-06-09
- mediumCVE-2026-56131: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from wit…msrc · 2026-06-09
- mediumCVE-2026-50219: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,…msrc · 2026-06-09
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