# CVE-2026-49263: Capstone WASM `br_table` instruction-size truncation can cause no-progress disassembly and parser desynchronization

> Attacker-supplied WebAssembly bytes can cause infinite loops or parser desynchronization in Capstone, leading to denial of service.

- **Severity:** Low 2.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** AZL-95979, AZL-96734, AZL-96743, BELL-CVE-2026-49263, DEBIAN-CVE-2026-49263, GHSA-5m9f-vqcm-g5pr, UBUNTU-CVE-2026-49263

## What is CVE-2026-49263?

CVE-2026-49263 is a low-severity vulnerability in capstone-engine capstone, published on 14 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### 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.

Weakness: CWE-197 (Numeric Truncation Error)

## Which versions are affected by CVE-2026-49263?


## How do I fix CVE-2026-49263?

Upgrade to a fixed version.

## Is CVE-2026-49263 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49263 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49263 and fix it if it is affected.

What it is: CVE-2026-49263 is a low-severity vulnerability in capstone-engine capstone, published on 14 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49263 exists.

Affected product: capstone-engine capstone. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-49263/ (Markdown: https://insights.sbomify.com/CVE-2026-49263/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49263
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49263
- OSV: https://osv.dev/vulnerability/CVE-2026-49263

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49263/
Summaries are generated and may contain mistakes; the official description above is the record.