CVE-2026-32740

import struct # Proof of Concept (Conceptual) for CVE-2026-32740 # This script demonstrates the logic to construct a malicious HEIF/AVIF file structure # that triggers the heap buffer overflow in libheif < 1.22.0 # The vulnerability is triggered by a 1x4 grid of odd-height tiles. def create_malicious_heif(filename): with open(filename, 'wb') as f: # HEIF File Header (ftyp) f.write(b'\x00\x00\x00\x20ftypheic') # ... (Complex HEIF structure omitted for brevity) ... # Conceptual Grid Image Item Box construction # The goal is to define a grid with 1 row and 4 columns # where tile heights are odd numbers (e.g., 5x5, 5x5, 5x5, 5x5) # This configuration triggers the 64-byte chroma overflow. grid_height = 5 # Odd height grid_width = 5 # Width rows = 1 columns = 4 # Writing the grid item properties (simplified) # In a real exploit, precise offsets and box sizes are required. print(f"Constructing malicious grid: {rows}x{columns}, Tile Size: {grid_width}x{grid_height}") print(f"Writing to: {filename}") print("Note: This is a conceptual stub. A real file requires valid ISO Base Media File Format boxes.") if __name__ == "__main__": create_malicious_heif("exploit.heic")

{"cve": {"id": "CVE-2026-32740", "sourceIdentifier": "[email protected]", "published": "2026-05-19T20:16:18.917", "lastModified": "2026-05-20T14:17:02.530", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "libheif is a HEIF and AVIF file format decoder and encoder. Versions 1.21.2 and prior contain a heap-buffer-overflow (write) vulnerability in the grid tile compositing, allowing an attacker to write 64 bytes of fully attacker-controlled data past the end of a chroma plane heap allocation by crafting a HEIF/AVIF file with a 1×4 grid of odd-height tiles. The overflow is triggered during normal image decoding with default build configuration. The written bytes are chroma (Cb/Cr) pixel values from the attacking tile, giving the attacker full control over the overflow content. This issue has been fixed in version 1.22.0."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-787"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:struktur:libheif:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.22.0", "matchCriteriaId": "CB01CAAF-1D64-461B-8CC0-3CF2FBAC60A5"}]}]}], "references": [{"url": "https://github.com/strukturag/libheif/releases/tag/v1.22.0", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/strukturag/libheif/security/advisories/GHSA-frfr-f3vg-2g6j", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/strukturag/libheif/security/advisories/GHSA-frfr-f3vg-2g6j", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}