CVE-2026-49263

CVE-2026-49263 · Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 2.0 · Low · EPSS 0.2%

Published

2026-08-14T17:49:36.804Z

Updated

2026-08-17T19:52:03.982Z

Stack: system

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