Vulnerability · Published Jun 21, 2026 · Assigned by mitre
CVE-2026-56403
Medium 6.9
In plain English
A medium-severity integer overflow in libexpat from libexpat project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)6.9Medium
Exploit odds (30 days)0.2%top 93.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
libexpat before 2.8.2 has an integer overflow in storeAtts.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.21 | expat | 2.8.2-r0 | ALPINE-CVE-2026-56403 |
| Alpine:v3.22 | expat | 2.8.2-r0 | ALPINE-CVE-2026-56403 |
| Alpine:v3.23 | expat | 2.8.2-r0 | ALPINE-CVE-2026-56403 |
| Alpine:v3.24 | expat | 2.8.2-r0 | ALPINE-CVE-2026-56403 |
| Debian:12 | expat | 2.5.0-1+deb12u3 | DEBIAN-CVE-2026-56403 |
| Debian:13 | expat | 2.8.2-1~deb13u1 | DEBIAN-CVE-2026-56403 |
| Debian:14 | expat | 2.8.2-1 | DEBIAN-CVE-2026-56403 |
| Ubuntu:22.04:LTS | cadaver | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | cadaver | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | cadaver | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | cadaver | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | cadaver | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | expat | 2.4.7-1ubuntu0.8 | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | expat | 2.4.7-1ubuntu0.8 | USN-8790-1 |
| Ubuntu:24.04:LTS | expat | 2.6.1-2ubuntu0.5 | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | expat | 2.6.1-2ubuntu0.5 | USN-8790-1 |
| Ubuntu:25.10 | expat | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | expat | 2.7.4-1ubuntu0.1 | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | expat | 2.7.4-1ubuntu0.1 | USN-8790-1 |
| Ubuntu:22.04:LTS | insighttoolkit4 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | libxmltok | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | libxmltok | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | matanza | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | matanza | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | matanza | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | matanza | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | matanza | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | swish-e | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | swish-e | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | tdom | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | tdom | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | tdom | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | tdom | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | tdom | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:22.04:LTS | wbxml2 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:24.04:LTS | wbxml2 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | wbxml2 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | wbxml2 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | wbxml2 | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:25.10 | xmlrpc-c | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.04:LTS | xmlrpc-c | no fix listed | UBUNTU-CVE-2026-56403 |
| Ubuntu:26.10 | xmlrpc-c | no fix listed | UBUNTU-CVE-2026-56403 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| libexpat project | libexpat | 0 – before 2.8.2 |
Weakness: CWE-190 · Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L