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OpenAdvisories
Low · 2.0 CVE-2026-49263 EUVD-2026-58747

Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization

Published Aug 14, 2026 · Updated Aug 17, 2026 · Assigned by GitHub_M

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

VendorProductAffectedFixed
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.

ReleasePackageFixed inAdvisory
Debian 14 capstone No fix yet —
Debian 13 capstone No fix yet —
Debian 12 capstone No fix yet —
ReleasePackageFixed inAdvisory
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)
ReleasePackageFixed inAdvisory
Ubuntu 18.04 LTS capstone No fix yet —
Ubuntu 16.04 LTS capstone No fix yet —
ReleasePackageFixed inAdvisory
Red Hat Hardened Images 1 capstone +4 5.0.8-0.5.hum1 RHSA-2026:81540

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 capstone No fix yet —
Azure Linux 3 rust 1.75.0-30 —

Advisories 1

References