CVE-2023-27997UnknownPublished 15 Feb 2026

tlp clear · KRVTZ-NET IDS alerts for 2026-02-15

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 15, 2026, report ongoing reconnaissance activity targeting Fortinet FortiOS VPN devices via repeated GET requests to the /remote/logincheck endpoint. This activity is linked to CVE-2023-27997, a vulnerability that allows unauthenticated attackers to probe VPN login endpoints remotely. While no active exploits or ransomware campaigns are currently tied to these alerts, the scanning indicates attackers are gathering information for potential future exploitation. The immediate severity is low, but unpatched vulnerabilities could lead to unauthorized access or denial of service. Organizations, particularly in Europe where Fortinet VPNs are prevalent, should prioritize patching and hardening VPN infrastructure to mitigate risk.

Impact

The vulnerability CVE-2023-27997 allows unauthenticated attackers to remotely probe Fortinet FortiOS VPN login endpoints, potentially enabling unauthorized access or denial of service if exploited. The ongoing reconnaissance activity increases the risk of future exploitation. Immediate impact is low as no active exploits or ransomware campaigns are currently associated, but the potential impact is significant if the vulnerability is exploited.

Defensive guidance

Organizations should prioritize monitoring and hardening Fortinet FortiOS VPN infrastructure, including restricting access to the /remote/logincheck endpoint where possible, implementing network-level protections, and maintaining vigilant detection of reconnaissance activity. Early detection and response are critical to prevent escalation to more damaging attacks.

Summary

KRVTZ-NET IDS detected reconnaissance activity on February 15, 2026, targeting Fortinet FortiOS VPN devices by sending repeated GET requests to the /remote/logincheck endpoint associated with CVE-2023-27997. This vulnerability permits unauthenticated remote probing of VPN login endpoints, which could lead to unauthorized access or denial of service if exploited. Multiple IPv4 and IPv6 addresses were identified as sources of scanning, alongside other reconnaissance behaviors such as HTTP User-Agent scanning and requests to hidden environment files. Although no active exploitation or ransomware campaigns are currently linked, the persistent scanning suggests attackers are gathering intelligence for potential future attacks. The vulnerability is known and listed in the CISA KEV catalog since June 2023.

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 8

2001:470:1:332::9ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
167.94.138.188- i Censys - HTTP User-Agent Scanner
167.94.138.185- i Censys - HTTP User-Agent Scanner
213.209.159.55ET INFO Request to Hidden Environment File - Inbound
113.165.121.239ET SCAN Google Webcrawler User-Agent (Mediapartners-Google)
191.96.67.196ET INFO Request to Hidden Environment File - Inbound
2001:470:1:fb5::280ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
2602:80d:1003::26- i Censys - HTTP User-Agent Scanner

Community reviews

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Exploitation evidence

Timeline

What to do

Description

AI analysisMachine-generated, updated 25 Oct 2026, 21:15 UTC

WeaknessesCWE-122

Indicators of compromise

IP addresses 8

Community reviews

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