CVE-2026-47751
Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration
Impact
Claude Code Action is a general-purpose GitHub action that runs Claude Code on GitHub pull requests and issues. Prior to 1.0.74, because the action checked out attacker-controlled pull request head branches, read .mcp.json from the working directory via default setting sources, and unconditionally enabled all project MCP servers via enableAllProjectMcpServers, an attacker who opened a pull request containing a malicious .mcp.json file could achieve arbitrary code execution on the GitHub Actions runner and exfiltrate secrets available to the workflow (such as API keys and tokens) when a privileged user or an automatic trigger invoked the Claude action on the pull request. This issue is fixed in version 1.0.74, which restores .claude/ and .mcp.json from the pull request base branch before the CLI runs.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| actions | anthropics/claude-code-action | < 1.0.74 | 1.0.74 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/anthropics/claude-code-action/commit/9ddce40de8c1ab71fb6303a125fdad0968dc1312
- https://github.com/anthropics/claude-code-action/pull/1066
- https://github.com/anthropics/claude-code-action/releases/tag/v1.0.74
- https://github.com/anthropics/claude-code-action/security/advisories/GHSA-8q5r-mmjf-575q
- https://github.com/advisories/GHSA-8q5r-mmjf-575q
- https://nvd.nist.gov/vuln/detail/CVE-2026-47751