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CVE-2026-47751

Claude Code Action: Malicious MCP Server Configuration in PRs Enables Remote Code Execution and Secret Exfiltration

MEDIUM
5.3
CVSS Score
Published: July 16, 2026 at 03:59 PM UTC
Updated: October 24, 2026 at 08:10 PM UTC
1 product affected across 1 vendorClaude Code Action

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.8%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Claude Code Action· Anthropics
90%
v < 1.0.74
Affected range stops below 1.0.74, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

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

SSVC — Action Prioritization

SSVCNo known exploitAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMGitHub_M
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-78CWE-200

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