CVE-2026-47751Medium▾ SunlitClaude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration
▾ Sunlit zone — Low / medium · no exploitation signal
impact 27.5 · likelihood 0.2 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 30.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.6%
0.6% → 0.8%
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.
Users 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
Claude Code thanks hackerone.com/reptou for reporting this issue.
anthropics/claude-code-action < 1.0.74Upgrade to a patched release:
anthropics/claude-code-action 1.0.74Connected by shared product, vendor, weakness, or advisory.
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