{"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":"Due to the combination of checking out PR head branches (attacker-controlled), reading `.mcp.json` from the working directory via default setting sources, and unconditionally enabling all project MCP servers via `enableAllProjectMcpServers`, it was possible for an attacker who opened a PR containing a malicious `.mcp.json` file to achieve arbitrary code execution on the GitHub Actions runner. This could lead to exfiltration of secrets available to the workflow (such as API keys and tokens) when a privileged user triggered the Claude action on the PR. Exploiting this required the ability to open a pull request against a repository using the claude-code-action and a privileged user or automatic trigger to invoke the action on that PR.\n\nUsers pinned to a vulnerable version of claude-code-action are advised to update to the latest version. Users referencing anthropics/claude-code-action@v1, anthropics/claude-code-action@beta, anthropics/claude-code-action@main, or other non-pinned tags will have received this fix already\n\nClaude Code thanks hackerone.com/reptou for reporting this issue.","published":"2026-07-16T15:59:29.885Z","modified":"2026-10-21T02:57:56.266223454Z","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"},{"type":"PACKAGE","url":"https://github.com/anthropics/claude-code-action"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:57:56.266223454Z"}}