CVE-2026-76957: libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks

Q: How do I fix CVE-2026-76957?

libexpat: upgrade to 2.8.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-76957 being exploited?

CVE-2026-76957 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-2026-76957 affect?

CVE-2026-76957 affects libexpat. Severity is medium (CVSS 4.9). 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.

Q: How urgent is CVE-2026-76957?

Priority 17/100. No elevated risk signals yet.

Routine

MEDIUM 4.9UPGRADE

CVE-2026-76957 is a medium-severity flaw (CVSS 4.9) affecting libexpat. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libexpat before 2.8.4 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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.9 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-416
Published	2026-08-20
Last modified	2026-09-08

Publisher (CNA): MITRE · Vendor: libexpat project

Last updated 2026-09-08 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-20 05:16 UTCPublished CVE record published
2026-09-08 20:56 UTCUpdated Record last modified

libexpat project libexpat UPGRADE

Affected: < 2.8.4

Fixed in: 2.8.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libexpat || rpm -q libexpat || libexpat --version

2. UPGRADE to 2.8.4 (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-2026-76957?

libexpat: upgrade to 2.8.4. Exact commands for each OS are on this page.

Is CVE-2026-76957 being exploited?

CVE-2026-76957 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-2026-76957 affect?

CVE-2026-76957 affects libexpat. Severity is medium (CVSS 4.9). 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.

How urgent is CVE-2026-76957?

Priority 17/100. No elevated risk signals yet.

Related CVEs

CVE-2026-56132 MEDIUM 6.9 UPGRADE In libexpat before 2.8.2, there is a heap-based buffer overflow in doProlog in xmlparse.c because scaffold bac
CVE-2026-56131 MEDIUM 4.9 UPGRADE libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in
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

References

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