CVE-2026-56407

libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textLen.

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-2026-56407 is rated Low Risk (28/100): 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-2026-56407

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-2026-56407

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.9 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/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:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
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.
 1.4 5.5 [email protected]

Weakness enumeration for CVE-2026-56407

GitHub Security Advisory for CVE-2026-56407

GHSA-r8qx-5vfx-8w6r · Severity: medium — libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and...

OS Trackers for CVE-2026-56407

vendor priority summary link
debian not yet assigned CVE-2026-56407 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-2026-56407
suse medium CVE-2026-56407 severity moderate: SUSE including 282 source package names (cmake, libkpathsea6, …), 2716 product×package rows across 23 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (23 product lines)): Known Not Affected 2716. https://www.suse.com/security/cve/CVE-2026-56407/
ubuntu medium CVE-2026-56407 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-2026-56407

Affected software / configurations for CVE-2026-56407

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

References for CVE-2026-56407

URL Tags
https://github.com/libexpat/libexpat/pull/1262 Patch Issue Tracking
cvelogic Threat Intelligence