PatchTheCVECVE-2026-56403: libexpat before 2.8.2 has an integer overflow in storeAtts.
26
Routine
MEDIUM 6.9UPGRADE
CVE-2026-56403 is a medium-severity flaw (CVSS 6.9) affecting libexpat. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
libexpat before 2.8.2 has an integer overflow in storeAtts.
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.9 (Medium) |
| Attack vector | Local |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.2% (top 94%) |
| CISA exploited list | No |
| Weakness | CWE-190 |
| Published | 2026-06-21 |
| Last modified | 2026-10-25 |
Publisher (CNA): MITRE · Vendor: libexpat project
Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
libexpat project libexpat UPGRADE
Affected: < 2.8.2
Fixed in: 2.8.2
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy libexpat || rpm -q libexpat || libexpat --version
2. UPGRADE to 2.8.2 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade libexpat
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade libexpat
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-56403?
libexpat: upgrade to 2.8.2. Exact commands for each OS are on this page.
Is CVE-2026-56403 being exploited?
CVE-2026-56403 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-56403 affect?
CVE-2026-56403 affects libexpat. Severity is medium (CVSS 6.9). libexpat before 2.8.2 has an integer overflow in storeAtts.
How urgent is CVE-2026-56403?
Priority 26/100. No elevated risk signals yet.
Related CVEs
- CVE-2026-56406 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in
- CVE-2026-56407 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textL
- CVE-2026-56404 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in addBinding.
- CVE-2026-56405 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in getAttributeId.
- CVE-2026-56408 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in copyString.