CVE-2026-84383 libheif: Heap buffer overflow in `scale_nearest_neighbor()` via duplicate Alpha planes from nested `iden`/`auxl` items
A heap buffer overflow in libheif allows remote attackers to execute arbitrary code or cause denial of service via crafted HEIF/AVIF files.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-84383?
CVE-2026-84383 is a critical memory corruption vulnerability in strukturag libheif, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
libheif is a HEIF and AVIF file format decoder and encoder. From 1.22.0 until 1.23.2, a crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can make HeifPixelImage::transfer_channel_from_image_as() append duplicate Alpha planes with different bit depths to m_storage. HeifPixelImage::scale_nearest_neighbor() in libheif/image/pixelimage.cc allocates the destination Alpha plane using the first plane's 8-bit depth, then iterates a later 10-bit or 12-bit Alpha component and writes uint16_t samples into the same 8-bit allocation. The output geometry controls the overflow extent and the encoded sample values control the data written, allowing a remote file processed by heif_decode_image() to cause a heap out-of-bounds write. This issue is fixed in version 1.23.2.
Weakness: CWE-787
Which versions are affected by CVE-2026-84383?
How do I fix CVE-2026-84383?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-84383 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84383 exists.
Public exploit code: 2 proofs of concept on GitHub.
Sources
Also known as BELL-CVE-2026-84383, DEBIAN-CVE-2026-84383, GHSA-g89c-p67h-r497, MINI-2ghf-3gv3-g7xj.