{"id":"CVE-2026-47751","aliases":["GHSA-8q5r-mmjf-575q"],"url":"https://o3.security/vulnerability/CVE-2026-47751","summary":"Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration","details":"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.","published":"2026-07-16T15:59:29.885Z","modified":"2026-08-12T03:51:45.585623549Z","cvss":null,"epss":{"score":0.00766,"percentile":0.53035,"asOf":"2026-09-02"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"GitHub Actions","name":"anthropics/claude-code-action","fixedVersion":"1.0.74"}],"fix":{"url":"https://github.com/anthropics/claude-code-action/commit/9ddce40de8c1ab71fb6303a125fdad0968dc1312","label":"anthropics/claude-code-action@9ddce40"},"references":[{"type":"WEB","url":"https://github.com/anthropics/claude-code-action/releases/tag/v1.0.74"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47751.json"},{"type":"ADVISORY","url":"https://github.com/anthropics/claude-code-action/security/advisories/GHSA-8q5r-mmjf-575q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47751"},{"type":"FIX","url":"https://github.com/anthropics/claude-code-action/commit/9ddce40de8c1ab71fb6303a125fdad0968dc1312"},{"type":"FIX","url":"https://github.com/anthropics/claude-code-action/pull/1066"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:45.585623549Z"}}