CVE-2026-56404: libexpat before 2.8.2 has an integer overflow in addBinding.

Q: How do I fix CVE-2026-56404?

libexpat: upgrade to 2.8.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-56404 being exploited?

CVE-2026-56404 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-56404 affect?

CVE-2026-56404 affects libexpat. Severity is medium (CVSS 6.9). libexpat before 2.8.2 has an integer overflow in addBinding.

Q: How urgent is CVE-2026-56404?

Priority 25/100. No elevated risk signals yet.

Routine

MEDIUM 6.9UPGRADE

CVE-2026-56404 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 addBinding.

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	0.1% (top 97%)
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

2026-06-21 16:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated 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.

Quick answers

How do I fix CVE-2026-56404?

libexpat: upgrade to 2.8.2. Exact commands for each OS are on this page.

Is CVE-2026-56404 being exploited?

CVE-2026-56404 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-2026-56404 affect?

CVE-2026-56404 affects libexpat. Severity is medium (CVSS 6.9). libexpat before 2.8.2 has an integer overflow in addBinding.

How urgent is CVE-2026-56404?

Priority 25/100. No elevated risk signals yet.

Related CVEs

CVE-2026-56403 MEDIUM 6.9 UPGRADE libexpat before 2.8.2 has an integer overflow in storeAtts.
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-2026-56405 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.

References

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