CVE-2026-49263

Summary

Capstone is a disassembly framework. Prior to version 6.0.0-Alpha9, Capstone's WebAssembly backend accepts attacker-controlled raw WASM instruction bytes through the public cs_disasm() and cs_disasm_iter() APIs. For a large but well-formed br_table instruction, the WASM decoder accumulates the immediate length in a wider local variable but returns it through a uint16_t instruction-size path. When the encoded instruction length is exactly 65,536 bytes, the size wraps to zero and cs_disasm() can repeatedly decode the same instruction without advancing. For larger lengths, cs_disasm_iter() advances into the middle of the br_table payload and decodes target bytes as subsequent instructions. This is an availability and parser-integrity issue. Version 6.0.0-Alpha9 patches the issue.

Affected Software

Weaknesses

• CWE-197: CWE-197: Numeric Truncation Error

References

• https://github.com/capstone-engine/capstone/security/advisories/GHSA-5m9f-vqcm-g5pr
• https://github.com/capstone-engine/capstone/blob/251c5bb4bc9bb92973e738ae3c5f4ef86f103356/ChangeLog#L102

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