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.
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.
Update anthropics/claude-code-action to 1.0.74 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanClaude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration affects anthropics/claude-code-action (actions). Severity is medium. 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.
AI coding agents often install or upgrade packages automatically in actions. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| anthropics/claude-code-actionactions | <1.0.74 | 1.0.74 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate anthropics/claude-code-action to 1.0.74 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanClaude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration affects anthropics/claude-code-action (actions). Severity is medium. 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.
AI coding agents often install or upgrade packages automatically in actions. A medium vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| anthropics/claude-code-actionactions | <1.0.74 | 1.0.74 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard