CVE-2026-56131: libexpat_project libexpat Use After Free
CVSS: 4.9v3.1MediumAnalyzed
AliasesALPINE-CVE-2026-56131UBUNTU-CVE-2026-56131DEBIAN-CVE-2026-56131CGA-4ccm-2pg9-h2rrCGA-6875-3r8f-7rvpCGA-6rvh-4h2f-pxhqCGA-hxc8-hjvg-cr29CGA-q3vh-x3ph-hvqfCGA-q7j8-7mrm-5v96CGA-w935-xhp8-rp88CGA-x2m3-cqr4-xpcp
Published 19-06-2026Last modified 22-06-2026
Vulnerability summary
CVE-2026-56131 is a medium (CVSS 4.9) Use After Free vulnerability in libexpat_project libexpat. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 6.6% of scored vulnerabilities.
CVSS score
4.9/10
010
Medium · v3.1 (CVE.org)EPSS score
0.18%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 10 · Related 9Timeline
- 19-06-2026PublishedVulnerability first disclosed.
- 22-06-2026Last modifiedVulnerability information updated.
Description
libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).
CVSS metrics
7 scores · 7 sources · 1 versionMedium 4.9Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:LSourcesAll 7 agree
- OSV · AlpineEcosystem advisory · calculated4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- OSV · UbuntuEcosystem advisory · calculated4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- OSV · DebianEcosystem advisory · calculated4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- OSV · WolfiEcosystem advisory · calculated4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- OSV · ChainguardEcosystem advisory · calculated4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
- NVDNIST4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
EPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
7%
Versus all other CVEs
30-day change
0.00 pp
From 0.18% on 19-09-2026
19-09-202619-10-2026
EPSS score0.18%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu16 products
- ayttmAll versions (No fix recorded)
- cableswigAll versions (No fix recorded)
- cadaverAll versions (No fix recorded)
- coin3All versions (No fix recorded)
- expat< 2.1.0-4ubuntu1.4+esm13 | < 2.1.0-7ubuntu0.16.04.5+esm14 | < 2.2.5-3ubuntu0.9+esm5 | < 2.2.9-1ubuntu0.8+esm3 | < 2.4.7-1ubuntu0.9 | < 2.6.1-2ubuntu0.6 | All versions (No fix recorded) | < 2.7.4-1ubuntu0.2
Chainguard4 products
- expat< 2.8.2-r0
- expat-dev< 2.8.2-r0
- expat-doc< 2.8.2-r0
- libexpat1< 2.8.2-r0
Wolfi4 products
- expat< 2.8.2-r0
- expat-dev< 2.8.2-r0
- expat-doc< 2.8.2-r0
- libexpat1< 2.8.2-r0
Alpine1 product
- expat< 2.8.2-r0
Debian1 product
- expat< 2.5.0-1+deb12u3 | < 2.8.2-1~deb13u1 | < 2.8.2-1
Libexpat_project1 product
- libexpat< 2.8.2
6 vendors · 27 products
