[UPDATE] [mittel] libexpat: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

CSIRTS triage

What

A local attacker can exploit multiple vulnerabilities in libexpat to conduct an unspecified attack, potentially including arbitrary code execution, data manipulation, bypassing security measures, disclosing confidential information, or causing a Denial of Service condition.

Who is affected

Users of libexpat.

Urgency

Remediation is medium urgency due to the wide range of potential impacts.

Action

Update to the latest version of libexpat to mitigate these vulnerabilities.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

CERT-Bund (BSI) Security Advisories (DE · national-cert · site)

Severity

medium

Published

2026-09-10

Exploitation

Not in CISA KEV at last sync

Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-2025

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-2026-502190.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564030.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564040.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564050.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564060.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564070.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564080.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564090.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564100.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.
• Low exploitation riskCVE-2026-564110.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 4% of all EPSS-scored CVEs.

Referenced CVEs

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

• unknownDSA-6404-1 expat - security updatedebian
• mediumCVE-2026-56405: libexpat before 2.8.2 has an integer overflow in getAttributeId.msrc
• mediumCVE-2026-56411: xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION declarat…msrc
• mediumCVE-2026-56407: libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue …msrc
• mediumCVE-2026-56410: xmlwf in libexpat before 2.8.2 has an integer overflow in resolveSystemId.msrc
• mediumCVE-2026-56404: libexpat before 2.8.2 has an integer overflow in addBinding.msrc
• mediumCVE-2026-56409: xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputD…msrc
• mediumCVE-2026-50219: libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse,…msrc
• mediumCVE-2026-56403: libexpat before 2.8.2 has an integer overflow in storeAtts.msrc
• mediumCVE-2026-56406: libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check tha…msrc
• mediumCVE-2026-56412: libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks ha…msrc

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.

• low[UPDATE] [niedrig] libexpat: Mehrere Schwachstellen ermöglichen Denial of Servicecert-bund · 2026-09-04
• mediumCVE-2026-76957: libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, …nvd · 2026-08-20
• mediumCVE-2026-76956: In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads …nvd · 2026-08-20
• highCVE-2026-76956: In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads …msrc · 2026-08-11
• mediumCVE-2026-72522: libexpat before 2.8.3 has an out-of-bounds read and resultant infinite loop because low surrog…msrc · 2026-08-11
• mediumCVE-2026-76957: libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, …msrc · 2026-08-11

More from CERT-Bund (BSI) Security Advisories

• medium[NEU] [mittel] Microsoft Edge: Schwachstelle ermöglicht Cross-Site Scripting2026-09-14
• medium[NEU] [mittel] Citrix Systems Workspace App Windows: Mehrere Schwachstellen ermöglichen nicht spezifizierten A…2026-09-14
• medium[NEU] [mittel] wpa_supplicant: Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen2026-09-14
• medium[NEU] [mittel] WP Royal Royal Elementor Addons: Schwachstelle ermöglicht Offenlegung von Informationen2026-09-14
• low[UPDATE] [niedrig] 7-Zip: Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen2026-09-14