CVE-2023-27997UnknownPublished 18 Feb 2026

tlp clear · KRVTZ-NET IDS alerts for 2026-02-18

Affects tlp clearSource CIRCL OSINT Feed

TLP:CLEAR, disclosure is not limited

Authoritative record:CVE-2023-27997· Critical 9.2

Exploited in the wild · used in ransomware campaigns · KEV due 4 Jul 2023 · 85% EPSS : block it and hunt for it in your logs now.

Data as of 26 Oct 2026, 08:30 UTC

CVSS base score

9.2Critical

How severe the flaw is on the 0–10 CVSS scale.

KEV deadline: 4 Jul 2023 US federal agencies must patch by this date; a sensible deadline for everyone else.
Ransomware: Used in ransomware campaigns
EPSS: 85.6% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 13 Jun 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: evidence found.
Listed in CISA KEV the same day as disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE ID reserved
by fortinet
9 Mar 202310:09 UTC, 96 days before disclosure
CVE published
on cve.org
13 Jun 202308:41 UTC, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed · ransomware use known
13 Jun 2023, the same day as disclosure
KEV remediation due
US federal deadline
4 Jul 2023, 21 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Apply updates per vendor instructions.

Description

The KRVTZ-NET IDS alerts from February 18, 2026, report reconnaissance activity targeting Fortigate VPN devices by sending repeated GET requests to the /remote/logincheck endpoint. This activity is consistent with attempts to exploit CVE-2023-27997, a vulnerability that allows unauthenticated attackers to bypass authentication and potentially execute arbitrary commands. Although no confirmed exploitation is reported, network traffic associated with SysJoker malware was also detected, indicating potential follow-on malware deployment. The alert is classified as low severity due to its reconnaissance nature and lack of confirmed exploitation. Organizations, especially in Europe, are advised to monitor for such activity and ensure Fortigate VPN devices are patched and secured.

Impact

If successfully exploited, CVE-2023-27997 allows unauthenticated attackers to bypass authentication on Fortigate VPN devices and potentially execute arbitrary commands, which could lead to full system compromise. The detection of SysJoker malware-related traffic suggests that exploitation attempts may be followed by malware deployment, increasing the risk of ransomware or other malicious activities. However, no confirmed exploitation is reported in this alert, so the immediate impact is limited to reconnaissance and scanning activity.

Defensive guidance

Meanwhile, monitoring for repeated GET requests to the /remote/logincheck endpoint and unusual network traffic patterns is recommended. Fortigate VPN devices should be kept up to date with the latest security updates. Strengthening VPN access controls and network defenses can help prevent successful exploitation. Since this is reconnaissance activity without confirmed exploitation, urgent remediation is not indicated but vigilance is advised.

Summary

This threat involves active reconnaissance targeting Fortigate VPN devices via repeated HTTP GET requests to the /remote/logincheck endpoint, consistent with attempts to exploit CVE-2023-27997. CVE-2023-27997 is an authentication bypass vulnerability that can lead to arbitrary command execution by unauthenticated attackers. The IDS alerts also detected network traffic linked to SysJoker malware, identified by its unique User-Agent string, suggesting possible malware deployment following initial access attempts. While exploitation is not confirmed, the presence of known ransomware campaign usage and inclusion in the CISA KEV catalog indicates the vulnerability is actively targeted. The activity is categorized as reconnaissance with low severity due to the absence of confirmed exploitation.

CWE-122Heap-based Buffer Overflow (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #16
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Pre-design: Use a language or compiler that performs automatic bounds checking.
Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Forced Integer Overflow (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

Indicators of compromise

IP addresses 2

2001:470:1:fb5:4db9:b7c7:f9ae:6e94ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
147.185.238.214ET MALWARE SysJoker User-Agent Observed

Community reviews

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Exploitation evidence

Timeline

What to do

Description

AI analysisMachine-generated, updated 25 Oct 2026, 21:14 UTC

WeaknessesCWE-122

Indicators of compromise

IP addresses 2

Community reviews

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