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.
- 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
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
Which versions are affected by CVE-2026-55893?
How do I fix CVE-2026-55893?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-55893 being exploited?
There is no known exploitation of CVE-2026-55893 in the wild and no public exploit code.
Sources
Also known as AZL-96894, AZL-97416, BELL-CVE-2026-55893, DEBIAN-CVE-2026-55893, GHSA-3hpv-wr3j-rxwh, UBUNTU-CVE-2026-55893.