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CVE-2026-56409 is an integer-overflow vulnerability in Expat's XML well-formedness utility prior to libexpat 2.8.2. The flaw occurs while constructing an output path when the utility is invoked with its output-directory option. An attacker may be able to cause size calculation or path-join arithmetic to wrap, resulting in an incorrectly sized allocation or subsequent memory corruption during output-path handling.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
11 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability addressed by Huawei EulerOS security advisory SA-2026-3583.
A vulnerability addressed by Huawei's EulerOS_SA-2026-3637 security advisory for EulerOS UVP 2.12.0.
An integer-overflow vulnerability in libexpat's xmlwf utility before version 2.8.2 when handling an output filename supplied with the -d option.
A vulnerability addressed by the EulerOS_SA-2026-3258 security update for EulerOS 2.0 Expat packages; no technical flaw details are provided.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.