Heap Buffer Overflow in stb_vorbis Library

Executive Summary

CVE-2026-89266 is a heap buffer overflow in stb_vorbis through version 1.22. The issue occurs in the start_decoder() function where the allocation size for codebook multiplicands is incorrectly truncated from size_t to int. This truncation leads to undersized memory allocation when processing malicious Ogg Vorbis files with large entries and dimensions values, causing out-of-bounds writes that may result in process crashes or heap corruption.

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Detection Guidance

Detecting this vulnerability requires analyzing Ogg Vorbis files processed by stb_vorbis v1.22 or earlier. Check for crashes or memory corruption when decoding audio files. Use static analysis tools to inspect stb_vorbis.c for improper size_t to int truncation in allocation functions like setup_malloc.

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Impact Analysis

This vulnerability can be exploited by attackers to craft malicious Ogg Vorbis files that trigger heap buffer overflows. This may lead to process crashes, heap corruption, denial of service, or potentially arbitrary code execution on systems using vulnerable versions of stb_vorbis, especially on 64-bit platforms where the truncation issue is more severe.

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Compliance Impact

This vulnerability could lead to data breaches or unauthorized memory access, which may violate GDPR's data protection requirements or HIPAA's safeguards for protected health information. Exploitation might result in exposure of sensitive data processed by affected applications.

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Mitigation Strategies

Update stb_vorbis to the latest version where the size_t to int truncation issue is fixed. If updating is not possible, avoid processing untrusted Ogg Vorbis files. Implement input validation to reject files with suspiciously large entries or dimensions values.

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