CVE-2026-47751
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk35th percentile - higher than 35% of all known CVEs
Summary
A vulnerability in the Claude Code Action GitHub action before version 1.0.74 allows an attacker to execute arbitrary code on the GitHub Actions runner by submitting a pull request with a malicious .mcp.json file. The action read this file from the PR branch by default and enabled all MCP servers, enabling theft of secrets (e.g., API keys and tokens) available in the workflow.
Risk Assessment
The organization risks compromise of the GitHub Actions runner and leakage of sensitive data (tokens, API keys) used in workflows, potentially leading to further attacks on infrastructure.
Recommendation
Immediately update Claude Code Action to version 1.0.74 or later, which restores .claude/ and .mcp.json from the PR base branch before the CLI runs.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

