Capstone SH disassembler `sh_disassemble` out-of-bounds read via crafted SH2A bytecode (CVE-2026-55894)
Published Last modified Sources: Red Hat, Msrc Update Guide, CVE.org
What is affected, what to do
Capstone is a disassembly framework. In 6.0.0-Alpha9 and earlier, Capstone's arch/SH/SHDisassembler.c sh_disassemble() function computes an idx value from a raw 16-bit instruction without ensuring it is within the active mode-specific decode[] function-pointer table.
Update Capstone-Engine Capstone to version 6.0.0-Alpha10.
- Affected
- Capstone-Engine Capstone
lt *..6.0.0-Alpha10
- Capstone-Engine Capstone
- Fixed in
- Capstone-Engine Capstone
6.0.0-Alpha10
- Capstone-Engine Capstone
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Metrics
6.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v4
6.8
CVSS v4
Severity Medium on the scale from 0 to 10.
Source: Red Hat, Msrc Update Guide, CVE.org
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 8.5
Show all metrics
- Severity
- Medium
Priority score
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 59.49
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 6.8
CVSS v4
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 6.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 8.5
- Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-125
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Capstone is a disassembly framework. In 6.0.0-Alpha9 and earlier, Capstone's arch/SH/SHDisassembler.c sh_disassemble() function computes an idx value from a raw 16-bit instruction without ensuring it is within the active mode-specific decode[] function-pointer table. An application using CS_ARCH_SH with CS_MODE_SH2A or CS_MODE_SH4A and CS_MODE_SHFPU can pass crafted bytecode through cs_disasm_iter() or cs_disasm(), causing the decode[idx] test to read outside the table and terminate the process with a segmentation fault. No code execution or information disclosure was demonstrated. This issue is fixed in version 6.0.0-Alpha10.
Source: redhat_csaf, Microsoft Security Update Guide, NVD (NIST), cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| capstone-engine | capstone |
|
|
Weakness classes (CWE)
CWE-125Out-of-bounds Read
Base
The product reads data past the end, or before the beginning, of the intended buffer.
Entry at MITRE CWE-125
References & sources
- github.comcapstone-engine/capstone/security/advisories/GHSA-gf2c-xwcp-hvf4x_refsource_CONFIRM
- github.comcapstone-engine/capstone/pull/2968x_refsource_MISC
- github.comcapstone-engine/capstone/pull/2969x_refsource_MISC
- github.comcapstone-engine/capstone/commit/09e76802380b9e94d9720c44458d9d5…x_refsource_MISC
- github.comcapstone-engine/capstone/commit/e17ee44a8307ea33375b4727ac4f987…x_refsource_MISC
- github.comcapstone-engine/capstone/releases/tag/6.0.0-Alpha10x_refsource_MISC
Reanalysis & status changes
Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.
CVE Translatednvd@nist.gov
- Translation: after Title: capstone de capstone-engine, Description: Capstone es un framework de desensamblaje. En 6.0.0-Alpha9 y versiones anteriores, la función sh_disassemble() de arch/SH/SHDisassembler.c de Capstone calcula un valor idx a partir de una instrucción bruta de 16 bits sin asegurar que esté dentro de la tabla de punteros a funciones decode[] activa y específica del modo. Una aplicación que utiliza CS_ARCH_SH con CS_MODE_SH2A o CS_MODE_SH4A y CS_MODE_SHFPU puede pasar bytecode manipulado a través de cs_disasm_iter() o cs_disasm(), haciendo que la prueba decode[idx] lea fuera de la tabla y termine el proceso con un fallo de segmentación. No se demostró ejecución de código ni revelación de información. Este problema está corregido en la versión 6.0.0-Alpha10.
CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0
- Reference: after https://github.com/capstone-engine/capstone/security/advisories/GHSA-gf2c-xwcp-hvf4
- SSVC: after {"id":"CVE-2026-55894","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalIm…