CVE-2026-49263

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in, but needs a user to act. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-14 18:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-18 20:05 UTC Last updatedMost recent change to the record

Details

Published

2026-08-14 18:17 UTC

Last modified

2026-09-18 20:05 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-197

Record status

Awaiting Analysis

Attack profile CVSS 4.0 · 2.0

Attack vector

Local

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

Passive

Confidentiality

None

Integrity

Low

Availability

Low