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CVE-2026-84383 is a heap out-of-bounds write in libheif versions 1.22.0 through 1.23.1. A crafted HEIF, HEIC, or AVIF item graph using nested iden and auxl references can cause duplicate Alpha planes with different bit depths to be added to image storage. During nearest-neighbor scaling, libheif allocates the destination Alpha plane according to an 8-bit plane, then can write 16-bit samples from a later 10-bit or 12-bit Alpha component into that allocation. The output geometry influences the overflow extent and encoded sample values influence the overwritten data.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This 17-file repository is a Docker-based, marker-only end-to-end exploit lab for CVE-2026-84383/GHSA-g89c-p67h-r497 in libheif 1.23.1. Its central executable workflow is scripts/verify.sh, supported by Bash preflight and ImageMagick wrapper scripts, three Dockerfiles, and Compose configurations. The repository builds an internal-only Discourse, PostgreSQL, and Redis environment; no host port is published. It submits a crafted HEIC file through the real authenticated POST /uploads.json route, causing Discourse UploadCreator to invoke ImageMagick and its HEIF delegate. The documented chain is a nested auxiliary-image decoding corruption, deterministic freed-object reuse, a file-controlled libjpeg callback, stack pivot, and fixed marker-writing ROP chain. The exploit fixture itself is referenced under fixtures/ and integrity-checked, but its binary contents are not included in the supplied file listing. Dockerfile.noaslr and scripts/magick-noaslr-wrapper intentionally preload jemalloc and disable ASLR only for the ImageMagick child; the Compose overlay additionally removes Docker seccomp restrictions needed by setarch. Therefore this is a valid but operationally constrained RCE proof, not evidence of ASLR-bypassing exploitation in a standard deployment. Dockerfile.patched builds libheif 1.23.2, and verify.sh demonstrates a differential result: exploit uploads produce the UID-1000 marker twice on 1.23.1, while 1.23.2 returns HTTP 422 without a marker; a benign HEIC still converts to JPEG on the patched image. Cleanup removes temporary API keys, staged data, markers, containers, and volumes.
15 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A heap buffer overflow in libheif's scale_nearest_neighbor() processing of crafted nested image items.
A critical, remotely triggerable heap out-of-bounds write (CWE-787) in libheif versions 1.22.0 through before 1.23.2. Malicious HEIF, HEIC, or AVIF files with nested item-graph references can create duplicate Alpha planes with mismatched bit depths, causing 16-bit samples to be written into an allocation sized for an 8-bit Alpha plane. The stated CVSS v3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
A high-severity vulnerability affecting Struktur libheif. The supplied CVSS v3.0 vector is CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H, indicating a network-reachable issue with low attack complexity, no privileges or user interaction required, and high confidentiality, integrity, and availability impact.
A critical upstream libheif vulnerability that can potentially result in remote code execution on glibc-based Linux under certain conditions when untrusted image input is processed through sharp.
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