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CVE-2026-32740 is a heap-based out-of-bounds write in libheif grid-tile compositing, affecting versions 1.21.2 and earlier. A crafted HEIF or AVIF image containing a 1×4 grid of odd-height tiles can cause chroma-plane row calculations to write 64 bytes of attacker-controlled Cb/Cr pixel data beyond a chroma-plane heap allocation during normal decoding with the default build configuration. The vulnerable behavior is associated with tile copying into a grid image, including the HeifPixelImage::copy_image_to() path. A reported, build-specific exploit chain further uses memory disclosure and plane-map corruption to obtain a constrained write primitive and execute code in a narrowly profiled Next.js, sharp, libvips, and libheif deployment; this chain depends on exact native-library versions, allocator behavior, upload handling, and binary layout.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This 47-file repository is a working, profile-driven remote RCE proof of concept for CVE-2026-32740 in libheif AVIF grid processing as reached through a deliberately vulnerable Next.js/sharp application. Its primary entry point, exploit.py, repeatedly uploads an AVIF disclosure image and retrieves its optimized PNG output. Python classifiers inspect returned alpha-channel pixels for multiple libvips-relative pointers, select exactly one supported native-stack profile and ASLR base, and fail closed on absent or ambiguous evidence. Heap-calibration code then obtains the required two-byte fake-node selector before generating the destructive payload. The final chain in rce_payload.py creates a four-row AVIF grid designed to overflow a chroma plane, redirect the Cr plane, and write a library path immediately before libvips memcpy@GOT while replacing that GOT entry with the computed address of libvips's internal g_module_open_full loader. callback/callback.c is compiled locally into an ELF shared object, uploaded as x.jpg, and loaded by the hijacked call. Its constructor runs only /usr/bin/id and returns the proof output over a TCP callback with a per-attempt token. The repository explicitly indicates that exploitation normally terminates the target process. Supporting components include avif_grid.py for controlled AVIF/ISO-BMFF construction, strict profile manifests for stock, Ubuntu PIE, and Debian PIE native stacks, offline artifact verification, heap/layout diagnostics, regression tests, evidence from repeated fresh-process runs, and Dockerfiles for intentionally vulnerable Debian 13 and Ubuntu 26.04 labs. The lab exposes POST /api/upload and GET /api/optimize?file=NAME, stores uploads under uploads/, and processes selected files with sharp. The exploit is highly version- and layout-specific rather than a general-purpose exploit framework module.
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A claimed remote-code-execution vulnerability affecting a PIE-enabled Next.js/Node.js stack using sharp and libheif. The referenced description attributes exploitation to a pixel leak, a chosen-address write, and memcpy GOT hijacking.
A heap-buffer overflow in libheif's HEIF/AVIF grid-image tile-copying logic. Incorrect independent chroma-row rounding can produce an out-of-bounds controlled write. In the deliberately vulnerable Next.js/sharp test application, the report demonstrates remote code execution by combining the overflow with a libvips address disclosure, forged libheif plane metadata, a GOT overwrite, and loading an uploaded shared library.
A heap-buffer-overflow write vulnerability in libheif grid tile compositing affecting versions 1.21.2 and prior, triggered by a crafted HEIF/AVIF file during normal image decoding.
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