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 products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| capstone-engine | capstone | < 6.0.0-Alpha9 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | capstone | No fix yet | — |
| Debian 13 | capstone | No fix yet | — |
| Debian 12 | capstone | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | capstone | No fix yet | — |
| Ubuntu 26.04 LTS | capstone | No fix yet | — |
| Ubuntu 24.04 LTS | capstone | No fix yet | — |
| Ubuntu 22.04 LTS | capstone | No fix yet | — |
| Ubuntu 20.04 LTS | capstone | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | capstone | No fix yet | — |
| Ubuntu 16.04 LTS | capstone | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | capstone +4 | 5.0.8-0.5.hum1 | RHSA-2026:81540 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | capstone | No fix yet | — |
| Azure Linux 3 | rust | 1.75.0-30 | — |
Advisories 1
- RHSA-2026:81540 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 17, 2026