UnknownPublished 27 Jan 2026

tlp clear · KRVTZ-NET IDS alerts for 2026-01-27

Affects tlp clearSource CIRCL OSINT Feed

TLP:CLEAR, disclosure is not limited

Mentions 1 CVE

Mentioned vulnerabilities

CVE-2023-27997

Description

KRVTZ-NET IDS alerts for 2026-01-27

Impact

For European organizations, the primary impact revolves around the potential compromise of Fortigate VPN devices, which are widely used for secure remote access. Successful exploitation of CVE-2023-27997 could lead to unauthorized access, data exfiltration, and lateral movement within corporate networks, undermining confidentiality and integrity. The reconnaissance and brute-force attempts may also degrade availability by overwhelming authentication services or triggering account lockouts. Given the critical role of VPNs in enabling remote work and secure communications, any disruption or breach could have significant operational consequences. Additionally, the presence of suspicious user-agent activity and brute-force attempts indicates a persistent threat environment that could escalate if vulnerabilities remain unpatched. European entities in sectors such as finance, government, healthcare, and critical infrastructure, which rely heavily on Fortigate VPNs, face heightened risks. The low severity rating suggests current risk is manageable but warrants proactive defense to prevent escalation.

Defensive guidance

1. Immediately verify and apply all available patches and firmware updates for Fortigate VPN devices to remediate CVE-2023-27997 and related vulnerabilities. 2. Implement strict access controls and multi-factor authentication (MFA) on VPN endpoints to reduce the risk of unauthorized access from brute-force attempts. 3. Monitor VPN login endpoints (/remote/logincheck) for unusual traffic patterns, including repeated GET requests and suspicious user-agent strings, using IDS/IPS and SIEM solutions. 4. Rate-limit authentication attempts and deploy account lockout policies to mitigate brute-force attacks while balancing usability. 5. Conduct regular threat hunting exercises focusing on the identified IP indicators and similar suspicious behaviors within network logs. 6. Restrict VPN access by IP whitelisting or geo-fencing where feasible to limit exposure to known malicious IP ranges. 7. Enhance network segmentation to contain potential breaches originating from compromised VPN access. 8. Educate security teams on recognizing reconnaissance activity and early exploitation signs specific to Fortigate VPNs. 9. Collaborate with threat intelligence providers to stay updated on emerging exploits and attacker tactics targeting Fortigate infrastructure. 10. Consider deploying web application firewalls (WAF) or VPN-specific security appliances that can detect and block exploitation attempts targeting vulnerable endpoints.

Indicators of compromise

IP addresses 7

2001:41d0:404:200::335bET HUNTING Suspicious User-Agent Observed (Mozilla/5.0 (Windows NT XX.X Win64 x64) AppleWebKit/XXX.XX)
165.154.179.204haproxy: 165.154.179.204 connecting to (submission/TCP) 15x in hour, possible bruteforcing.
2001:470:1:fb5:3fca:7434:e172:1361ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
110.93.150.192ET SCAN Naver Webcrawler User-Agent (Naver.me)
2001:470:2cc:1::1bfET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
51.91.109.26ET HUNTING Suspicious User-Agent Observed (Mozilla/5.0 (Windows NT XX.X Win64 x64) AppleWebKit/XXX.XX)
110.93.150.201ET SCAN Naver Webcrawler User-Agent (Naver.me)

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Description

AI analysisMachine-generated, updated 27 Jan 2026, 10:50 UTC

Indicators of compromise

IP addresses 7

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