DSA-6404-1 expat - security update
Multiple security issues were discovered in expat, an XML parsing C library, including integer overflows, out-of-bounds write, NULL pointer dereferences, excessive resource consumption, and memory corruption through re-entrant parser API calls, which may result in denial of service or potentially the execution of arbitrary code. https://security-tracker.debian.org/tracker/DSA-6404-1
CSIRTS triage
- What
- Multiple security issues may result in denial of service or arbitrary code execution.
- Who is affected
- Users of Expat are affected.
- Urgency
- Remediation is necessary, but the vulnerabilities are not actively exploited.
- Action
- Users should apply the security update.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://lists.debian.org/debian-security-announce/2026/msg00315.html
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.
- Moderate exploitation riskCVE-2025-593751.3% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 67% of all scored CVEs.
- Low exploitation riskCVE-2026-245150.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all scored CVEs.
- Low exploitation riskCVE-2026-252100.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all scored CVEs.
- Low exploitation riskCVE-2026-327760.16% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all scored CVEs.
- Low exploitation riskCVE-2026-327770.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 12% of all scored CVEs.
- Low exploitation riskCVE-2026-327780.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all scored CVEs.
- Low exploitation riskCVE-2026-410800.40% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 33% of all scored CVEs.
- Low exploitation riskCVE-2026-451860.44% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 36% of all scored CVEs.
- Low exploitation riskCVE-2026-502190.29% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 21% of all scored CVEs.
- Low exploitation riskCVE-2026-561310.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all scored CVEs.
Referenced CVEs
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- low[UPDATE] [low] libexpat: Multiple vulnerabilities allow denial of servicecert-bund
- low[UPDATE] [low] expat: Vulnerability allows Denial of Servicecert-bund
- high[UPDATE] [high] IBM HTTP Server: Multiple Vulnerabilitiescert-bund
- medium[UPDATE] [medium] libexpat: Multiple vulnerabilities allow unspecified attackcert-bund
- medium[UPDATE] [medium] expat: Multiple vulnerabilitiescert-bund
- high[NEW] [high] Dell integrated Dell Remote Access Controller: Multiple vulnerabilitiescert-bund
- low[UPDATE] [low] expat: Vulnerability allows Denial of Servicecert-bund
- unknownUSN-8520-1: Expat vulnerabilityubuntu
- high[NEW] [high] Dell PowerProtect Data Domain: Multiple vulnerabilitiescert-bund
- criticalSiemens SINEC OScisa
- mediumCVE-2026-50219: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,…msrc
- mediumCVE-2026-56406: libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check tha…msrc
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