{"id":"CVE-2026-47751","aliases":["GHSA-8q5r-mmjf-575q"],"title":"Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration","summary":"Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration","severity":"medium","cwe":["CWE-78","CWE-200"],"vendor":"anthropics","product":"anthropics/claude-code-action","ecosystem":"actions","affected":["anthropics/claude-code-action < 1.0.74"],"patched":["anthropics/claude-code-action 1.0.74"],"published":"2026-06-10","updated":"2026-06-10","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-8q5r-mmjf-575q","references":[{"url":"https://github.com/anthropics/claude-code-action/security/advisories/GHSA-8q5r-mmjf-575q"},{"url":"https://github.com/advisories/GHSA-8q5r-mmjf-575q"}],"tags":["ghsa","actions"],"ingestedAt":"2026-07-07T15:41:59.541Z","epss":0.00766,"epssPercentile":0.53536,"slug":"CVE-2026-47751","body":"## Overview\n\nDue 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.\n\n## Affected packages\n\n- `anthropics/claude-code-action < 1.0.74`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `anthropics/claude-code-action 1.0.74`","depth":"sunlit","depthScore":28,"depthScoreParts":{"impact":27.5,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}