Report · CIRCL OSINT FeedAbout CVE-2023-27997Published 21 Jan 2026

tlp clear · KRVTZ IDS alerts for 2026-01-21

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 · no patch yet : apply the vendor's fix or mitigations to tlp clear now.

Data as of 26 Oct 2026, 06:26 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.
Patch: Not yet available

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
2023-03-0910:09Z, 96 days before disclosure
CVE published
on cve.org
2023-06-1308:41Z, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed · ransomware use known
2023-06-13, the same day as disclosure
KEV remediation due
US federal deadline
2023-07-04, 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 2026-10-26.

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

KRVTZ IDS alerts from January 21, 2026, report network reconnaissance targeting Fortigate VPN devices, specifically repeated GET requests to the /remote/logincheck endpoint associated with CVE-2023-27997. This vulnerability allows unauthenticated attackers to bypass authentication and execute arbitrary commands. Additional suspicious scanning includes anomalous HTTP user-agent strings and attempts to access sftp-config.json files to discover exposed credentials. No active exploitation or public patches are currently reported. European organizations, especially in critical infrastructure, finance, and government sectors, are at increased risk. The threat level is medium due to the potential impact if exploited combined with ease of reconnaissance. Defenders should prioritize patching when available, restrict access, and secure credentials to mitigate risk.

Impact

Successful exploitation of CVE-2023-27997 can allow unauthenticated attackers to bypass authentication and execute arbitrary commands on Fortigate VPN devices, potentially leading to full system compromise. The reconnaissance activities increase the likelihood of exploitation attempts. The vulnerability is known to be leveraged in ransomware campaigns, elevating the risk to affected organizations. No active exploitation is currently reported, but the reconnaissance phase indicates increased targeting. The impact is significant for critical infrastructure, finance, and government sectors relying on Fortigate VPN appliances.

Mitigation

Currently, no patches or official fixes are available for CVE-2023-27997. Defenders should implement strict access controls to limit exposure of Fortigate VPN devices to untrusted networks. Monitoring for anomalous GET requests to /remote/logincheck and unusual HTTP user-agent strings is recommended to detect reconnaissance attempts. Secure management of credentials and restricting access to sftp-config.json files or similar sensitive configuration files is advised. Organizations should stay alert for vendor advisories regarding patches and apply them promptly once available.

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 5

2001:470:1:fb5::160ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
2620:96:e000::d9- i Censys - HTTP User-Agent Scanner
2600:3c02::2000:c5ff:fe30:d03bET HUNTING Suspicious User-Agent Observed (Mozilla/5.0 (Windows NT XX.X Win64 x64) AppleWebKit/XXX.XX)
188.166.226.108ET SCAN SFTP/FTP Password Exposure via sftp-config.json
45.79.252.178ET HUNTING Suspicious User-Agent Observed (Mozilla/5.0 (Windows NT XX.X Win64 x64) AppleWebKit/XXX.XX)

Community reviews

Loading reviews…

Exploitation evidence

Timeline

What to do

Description

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

WeaknessesCWE-122

Indicators of compromise

IP addresses 5

Community reviews

Related threats