Vulnerability · Published Aug 14, 2026 · Assigned by GitHub_M
CVE-2026-49263Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization
Low 2.0
In plain English
A low-severity security flaw in capstone from capstone-engine. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities).
Official description
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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | capstone | no fix listed | DEBIAN-CVE-2026-49263 |
| Debian:13 | capstone | no fix listed | DEBIAN-CVE-2026-49263 |
| Debian:14 | capstone | no fix listed | DEBIAN-CVE-2026-49263 |
| Ubuntu:22.04:LTS | capstone | no fix listed | UBUNTU-CVE-2026-49263 |
| Ubuntu:24.04:LTS | capstone | no fix listed | UBUNTU-CVE-2026-49263 |
| Ubuntu:26.04:LTS | capstone | no fix listed | UBUNTU-CVE-2026-49263 |
| Ubuntu:26.10 | capstone | no fix listed | UBUNTU-CVE-2026-49263 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| capstone-engine | capstone | < 6.0.0-Alpha9 |
Weakness: CWE-197 · Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N