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.
Published: 2026-08-14
Score: 2 Low
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Fri, 14 Aug 2026 19:45:00 +0000

Type Values Removed Values Added
First Time appeared Capstone-engine
Capstone-engine capstone
Vendors & Products Capstone-engine
Capstone-engine capstone

Fri, 14 Aug 2026 18:15:00 +0000

Type Values Removed Values Added
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.
Title Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization
Weaknesses CWE-197
References
Metrics cvssV4_0

{'score': 2, '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'}


Subscriptions

Capstone-engine Capstone
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-14T17:49:36.804Z

Reserved: 2026-05-28T14:33:01.180Z

Link: CVE-2026-49263

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-14T18:17:30.643

Modified: 2026-08-14T18:17:30.643

Link: CVE-2026-49263

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-14T19:30:04Z

Weaknesses