Quick answers
- Is CVE-2026-49263 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-49263 being exploited in the wild.
- How severe is CVE-2026-49263?
- Informational severity, published 14 August 2026.
- Which products and versions are affected?
- Capstone Capstone prior to 6.0.0-Alpha9.
- Is there a fix for CVE-2026-49263?
- A patch was published on 2026-05-27. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-49263 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-49263?
- Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an integer truncation bug in Capstone's WASM decoder's `br_table` instruction handler. The decoder accumulates instruction size in a 32-bit local variable but assigns it to a 16-bit output parameter without bounds checking. When a `br_table` instruction is exactly 65,536 bytes long, the size wraps to zero in the `uint16_t` field; larger instructions wrap to non-zero incorrect values. This causes `cs_disasm()` with unbounded count to loop indefinitely on the same instruction without advancing the buffer, or `cs_disasm_iter()` to skip into the middle of instruction payloads and decode garbage as subsequent instructions. The root cause is in `WASMDisassembler.c:601-610` where `*param_size = tmp_len + var_len` lacks overflow protection. No user interaction or authentication is required; any code that passes untrusted WASM bytecode to the disassembly APIs is affected. Version 6.0.0-Alpha9 patches the issue.
Affected products
- Capstone Capstone prior to 6.0.0-Alpha9
Timeline
- 2026-05-27: disclosed
- 2026-05-27: patched