CVE-2026-32738 libheif has a Heap OOB Read/SEGV Crash via Zero samples_per_chunk
A crafted HEIF file triggers an integer underflow leading to a null-pointer dereference and crash, causing denial of service in libheif.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-32738?
CVE-2026-32738 is a medium-severity vulnerability in strukturag libheif, published on 19 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
libheif is a HEIF and AVIF file format decoder and encoder. In versions 1.21.2 and below, a crafted 792-byte HEIF sequence file with samples_per_chunk=0 in the stsc box causes an unsigned integer underflow in the Chunk constructor (m_last_sample = 0 + 0 - 1 = UINT32_MAX), mapping all samples to an empty chunk and resulting in a denial of service. When any sample is accessed, the library reads from index 0 of an empty std::vector, causing a guaranteed SEGV (null-page read). The file parses successfully without producing an error; the crash occurs on the first frame access. This issue has been fixed in version 1.22.0.
Which versions are affected by CVE-2026-32738?
It affects 1 product.
Products include Struktur Libheif.
How do I fix CVE-2026-32738?
Upgrade to a fixed version.
Is CVE-2026-32738 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32738 exists.
Other vulnerabilities in strukturag libheif
Sources
Also known as ALPINE-CVE-2026-32738, BELL-CVE-2026-32738, DEBIAN-CVE-2026-32738, GHSA-7f2h-cmpf-v9ww, JLSEC-2026-570, ROOT-OS-DEBIAN-12-CVE-2026-32738 and 1 more.