CVE-2026-84383: strukturag libheif Out-of-bounds Write

Vulnerability summary

CVE-2026-84383 is a critical (CVSS 9.8) Out-of-bounds Write vulnerability in strukturag libheif. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48.1% of scored vulnerabilities.

Timeline

1. 18-09-2026
   PublishedVulnerability first disclosed.
2. 18-09-2026
   Last modifiedVulnerability information updated.

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.

• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.