Vulnerability · Published Jul 21, 2026 · Assigned by GitHub_M

CVE-2026-47251libheif has an incomplete fix for CVE-2026-3949: integer overflow bypass in vvdec_push_data2

Medium 6.8

In plain English

A medium-severity out-of-bounds read in libheif from strukturag. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities).

Severity (CVSS 4.0)6.8Medium

Exploit odds (30 days)0.2%top 94.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

libheif is a HEIF and AVIF file format decoder and encoder. The fix for CVE-2026-3949 (commit `b97c8b5`, PR #1712) introduced an integer overflow in the very security check it added. The check itself can be bypassed, allowing a crafted HEIF file with a VVC track to trigger the same out-of-bounds heap read that CVE-2026-3949 was meant to prevent. This is a separate, currently-unpatched vulnerability. Issue #1712 was closed as fixed without testing the edge case where `size` is near `UINT32_MAX`. Version 1.22.0 patches the issue.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	libheif	no fix listed	DEBIAN-CVE-2026-47251
Debian:13	libheif	no fix listed	DEBIAN-CVE-2026-47251
Debian:14	libheif	no fix listed	DEBIAN-CVE-2026-47251
Ubuntu:24.04:LTS	libheif	no fix listed	UBUNTU-CVE-2026-47251
Ubuntu:25.10	libheif	no fix listed	UBUNTU-CVE-2026-47251
Ubuntu:26.04:LTS	libheif	no fix listed	UBUNTU-CVE-2026-47251

Affected products (as reported)

Vendor	Product	Versions
strukturag	libheif	< 1.22.0

Weakness: CWE-125, CWE-190 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N

References

https://github.com/strukturag/libheif/security/advisories/GHSA-p6q9-fhf2-vj9v x_refsource_CONFIRM
https://github.com/strukturag/libheif/issues/1712 x_refsource_MISC