CVE-2026-56409

xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.

Published: 2026-06-21 Last update: 2026-06-23 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-56409 is rated Low Risk (26.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.10%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-56409

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-23 — 0.10% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-56409

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.0 5.5 [email protected]

Weakness enumeration for CVE-2026-56409

GitHub Security Advisory for CVE-2026-56409

GHSA-jhv6-83wh-9vj5 · Severity: medium — xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir...

OS Trackers for CVE-2026-56409

vendor priority summary link
debian not yet assigned CVE-2026-56409 not yet assigned priority: Debian including 1 source packages (expat), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-56409
ubuntu medium CVE-2026-56409 medium priority: Ubuntu including 23 source packages (apache2, apr-util, …), 163 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): needs-triage 77, not-affected 56, DNE 25, ignored 5. https://ubuntu.com/security/CVE-2026-56409

Affected software / configurations for CVE-2026-56409

Vendor Product Version Raw CPE
libexpat_project libexpat < 2.8.2 cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*

References for CVE-2026-56409

URL Tags
https://github.com/libexpat/libexpat/pull/1259 Patch Issue Tracking
cvelogic Threat Intelligence