# CVE-2026-55893: Capstone SH disassembler `set_reg_n` heap buffer overflow via crafted SH2A FPU bytecode

> A heap buffer overflow in the Capstone SH disassembler allows attackers to crash the process or potentially execute code via crafted bytecode.

- **Severity:** High 7.3 (`CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/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:** 20 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** AZL-96894, AZL-97416, BELL-CVE-2026-55893, DEBIAN-CVE-2026-55893, GHSA-3hpv-wr3j-rxwh, UBUNTU-CVE-2026-55893

## What is CVE-2026-55893?

CVE-2026-55893 is a high-severity memory corruption vulnerability in capstone-engine capstone, published on 20 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. In 6.0.0-Alpha9 and earlier, Capstone's arch/SH/SHDisassembler.c SH floating-point decoders such as opFADD, opFMUL, and opFSUB call set_reg() and set_reg_n() using sh_info.op.op_count without checking the fixed-size operands[] array. Repeated crafted instructions processed through cs_disasm_iter() or cs_disasm() with CS_ARCH_SH, CS_MODE_SH2A or CS_MODE_SH4A, CS_MODE_SHFPU, and CS_OPT_DETAIL can increment the operand count beyond the 176-byte sh_info allocation and perform a four-byte heap buffer overflow write. The corruption can crash the process and may enable code execution depending on heap layout. This issue is fixed in version 6.0.0-Alpha10.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-55893?


## How do I fix CVE-2026-55893?

Upgrade to a fixed version.

## Is CVE-2026-55893 being exploited?

There is no known exploitation of CVE-2026-55893 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55893 and fix it if it is affected.

What it is: CVE-2026-55893 is a high-severity memory corruption vulnerability in capstone-engine capstone, published on 20 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: There is no known exploitation of CVE-2026-55893 in the wild and no public exploit code.

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-2026-55893/ (Markdown: https://insights.sbomify.com/CVE-2026-55893/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55893
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55893
- OSV: https://osv.dev/vulnerability/CVE-2026-55893

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-55893/
Summaries are generated and may contain mistakes; the official description above is the record.