CVE-2026-76957: libexpat_project libexpat Use After Free
CVSS: 7.8v3.1HighAnalyzed
AliasesALPINE-CVE-2026-76957UBUNTU-CVE-2026-76957DEBIAN-CVE-2026-76957
Published 20-08-2026Last modified 20-08-2026
Vulnerability summary
CVE-2026-76957 is a high (CVSS 7.8) Use After Free vulnerability in libexpat_project libexpat. EPSS estimates a 0.11% chance of exploitation in the next 30 days, higher than 1% of scored vulnerabilities.
CVSS score
7.8/10
010
High · v3.1 (NVD)EPSS score
0.11%
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 11 · Related 8Timeline
- 20-08-2026PublishedVulnerability first disclosed.
- 20-08-2026Last modifiedVulnerability information updated.
Description
libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after-free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.
CVSS metrics
5 scores · 5 sources · 1 versionHigh 7.8Preferred score · NVD (NIST)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSources5 sources · 4.9–7.8
- CVE.orgCNA4.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:LDiffers
- OSV · AlpineEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.11%
Chance of exploitation in the next 30 days
Percentile
1%
Versus all other CVEs
30-day change
0.00 pp
From 0.11% on 19-09-2026
19-09-202619-10-2026
EPSS score0.11%
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 | < 2.7.4-1ubuntu0.2
Alpine1 product
- expat< 2.8.4-r0
Debian1 product
- expatAll versions (No fix recorded) | < 2.5.0-1+deb12u3 | < 2.9.0-1~deb13u1 | < 2.8.4-1
Libexpat_project1 product
- libexpat< 2.8.4
4 vendors · 19 products
