Affected versions of this package are vulnerable to Heap-based Buffer Overflow when the ReadHuffmanCodes() function is used. An attacker can craft a special WebP lossless file that triggers the ReadHuffmanCodes() function to allocate the HuffmanCode buffer with a size that comes from an array of precomputed sizes: kTableSize. The color_cache_bits value defines which size to use. The kTableSize array only takes into account sizes for 8-bit first-level table lookups but not second-level table lookups. libwebp allows codes that are up to 15-bit (MAX_ALLOWED_CODE_LENGTH). When BuildHuffmanTable() attempts to fill the second-level tables it may write data out-of-bounds. The OOB write to the undersized array happens in ReplicateValue.
Notes:
This is only exploitable if the color_cache_bits value defines which size to use.
This vulnerability was also published on libwebp CVE-2023-5129
Changelog:
2023-09-12: Initial advisory publication
2023-09-27: Advisory details updated, including CVSS, references
2023-09-27: CVE-2023-5129 rejected as a duplicate of CVE-2023-4863