CVE-2026-56406: libexpat_project libexpat Integer Overflow or Wraparound
CVSS: 6.9v3.1MediumAnalyzed
AliasesALPINE-CVE-2026-56406UBUNTU-CVE-2026-56406DEBIAN-CVE-2026-56406CGA-3m5q-49vg-7qqxCGA-9hjg-94rg-vxf6CGA-ch7q-3xpg-3284CGA-f28r-cwrh-gw29CGA-mhgx-5wq2-9gw9CGA-p34c-jj34-7f82CGA-vpcc-wcjw-3xhmCGA-xqmw-5w9m-9473
Published 21-06-2026Last modified 22-06-2026
Vulnerability summary
CVE-2026-56406 is a medium (CVSS 6.9) Integer Overflow or Wraparound vulnerability in libexpat_project libexpat. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 6.4% of scored vulnerabilities.
CVSS score
6.9/10
010
Medium · v3.1 (CVE.org)EPSS score
0.17%
0%100%
Low · +0.04 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 9 · Related 9Timeline
- 21-06-2026PublishedVulnerability first disclosed.
- 22-06-2026Last modifiedVulnerability information updated.
Description
libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.
CVSS metrics
7 scores · 7 sources · 1 versionMedium 6.9Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:LSourcesAll 7 agree
- OSV · AlpineEcosystem advisory · calculated6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- OSV · UbuntuEcosystem advisory · calculated6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- OSV · DebianEcosystem advisory · calculated6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- OSV · WolfiEcosystem advisory · calculated6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- OSV · ChainguardEcosystem advisory · calculated6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
- NVDNIST6.9MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
EPSS trend
Probability
0.17%
Chance of exploitation in the next 30 days
Percentile
6%
Versus all other CVEs
30-day change
+0.04 pp
From 0.14% on 19-09-2026
19-09-202619-10-2026
EPSS score0.17%
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
