Trojanized Claude Code VS Code extension (Anthropic.claude-code 2.1.312 and 2.1.313) in Cursor's extension marketplace planted an SSH bac…
Published Sources: pwn.watch
What is affected, what to do
Cursor says a maliciously modified build of Anthropic's Claude Code VS Code extension, Anthropic.claude-code 2.1.312 and 2.1.313 for macOS and Windows, was available in the Cursor IDE extension marketplace between about 2:27am and 1:35pm PT on Oct 29 2026, and that at most 5,000 users were affected. Cursor says the build was not developed by Anthropic and that no other extensions were tampered with.
The available sources name no fixed version. Check the vendor guidance in the references below.
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Metrics
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Priority
No value is available for this vulnerability.
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CVSS v3
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EPSS score
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Priority (0–325)
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- 30.00 Methodology
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
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
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- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
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
Cursor says a maliciously modified build of Anthropic's Claude Code VS Code extension, Anthropic.claude-code 2.1.312 and 2.1.313 for macOS and Windows, was available in the Cursor IDE extension marketplace between about 2:27am and 1:35pm PT on Oct 29 2026, and that at most 5,000 users were affected. Cursor says the build was not developed by Anthropic and that no other extensions were tampered with. On load, a loader prepended to extension.js collects host and user details, appends an attacker SSH key (comment svc-telemetry) to authorized_keys, tries to enable the local SSH service and open a reverse SSH tunnel to 134.209.82.225, installs persistence (LaunchAgent on macOS, a SysMon scheduled task or Startup script on Windows), and beacons to port 8099. Cursor says enabling SSH needs admin rights, so on most macOS and Windows hosts the tunnel step failed, but the key, persistence and beacon still happen. Cursor's Oct 30 update to its notice added 2.1.312 to the affected versions, so check for both. Cursor removed the malicious build, shut down and rebuilt its marketplace, rotated its keys, got the attacker server taken offline, and asks everyone to update to 2.1.314. OpenSourceMalware first reported the artifact as coming from Open VSX, then updated its write-up to say the compromise was in the Cursor marketplace and that the Open VSX and Microsoft Marketplace extensions and the npm package are not malicious. If you installed or updated to 2.1.312 or 2.1.313 in Cursor during that window, check authorized_keys for svc-telemetry, run Cursor's remediation script, rotate credentials from a clean machine, and consider rebuilding the host.
Source: pwn.watch