Capstone SH disassembler `set_reg_n` heap buffer overflow via crafted SH2A FPU bytecode

Published 2 mo ago 2026-08-20 · modified 20 d ago 2026-10-18 · JSON

CVSS

7.3

v4.0 · CNA

CISA KEV

not known exploited

EPSS

0.2%

percentile 8%

Public exploits

none known

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.

CISA SSVC assessment

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 2 mo ago 2026-08-21

Exploit prediction (EPSS)

0.19% probability of exploitation in the next 30 days, higher than 8% of all scored CVEs.

CVSS scores

Assigned by	Version	Score	Vector
CNA	4.0	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`
CNA	4.0	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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X`

Affected products

capstone-engine capstone

Classification

Weakness

CWE-122 Heap-based Buffer Overflow

References

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

Sources

CVE List: CVE-2026-55893
NVD: CVE-2026-55893

vulnwire keeps one entry per vulnerability: the CVE id wins, then GHSA; records that alias each other are merged. Machine-readable: JSON.

Summary