Vulnerability · Published Aug 18, 2026 · Assigned by GitHub_M
CVE-2026-62291libheif: Heap out of bounds write in libheif uncompressed encoder when writing images with mismatched auxiliary alpha dimensions
Medium 5.3
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 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
libheif is a HEIF and AVIF file format decoder and encoder. In 1.23.0 and earlier, a crafted image sequence with a 2x2 primary plane and a 256x256 auxiliary alpha plane can cause attacker-controlled heap corruption during a normal decode and re-encode workflow. Track_Visual::decode_next_image_sample() calls transfer_channel_from_image_as() without checking that the auxiliary alpha dimensions match the main frame. The resulting inconsistent image reaches heif_track_decode_next_image() and then heif_context_encode_image(). In unc_encoder::encode(), unc_encoder_component_interleave::encode_tile() sizes its buffer with compute_tile_data_size_bytes() using the primary dimensions but copies each component using its actual plane dimensions. The oversized alpha plane is therefore copied beyond the allocation, causing an out-of-bounds write; the inverse size mismatch can also produce an out-of-bounds read. This issue is fixed in version 1.23.1.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | libheif | 1.23.1-1 | DEBIAN-CVE-2026-62291 |
| Ubuntu:24.04:LTS | libheif | 1.17.6-1ubuntu4.8 | UBUNTU-CVE-2026-62291 |
| Ubuntu:24.04:LTS | libheif | 1.17.6-1ubuntu4.8 | USN-8683-1 |
| Ubuntu:26.04:LTS | libheif | 1.21.2-3ubuntu0.5 | UBUNTU-CVE-2026-62291 |
| Ubuntu:26.04:LTS | libheif | 1.21.2-3ubuntu0.5 | USN-8774-1 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| strukturag | libheif | < 1.23.1 |
Weakness: CWE-125, CWE-787 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L