Medium [CVE-2026-49263] Denial of Service and parser desynchronization via WebAssembly `br_table` instruction-size truncation

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.

A remote attacker could exploit this by providing a specially crafted `br_table` instruction. This could lead to a denial of service, where the disassembler gets stuck in a loop, or cause parser desynchronization, leading to incorrect disassembly of subsequent instructions.

Red Hat severity: Moderate — CVSS 6.8 (CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H). Weakness: CWE-190.

Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9; Red Hat Hardened Images; Red Hat OpenShift Container Platform 4. Red Hat does not currently list a fixing RHSA for this CVE.