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CVE-2023-27997UnknownPublished

tlp clear · KRVTZ-NET IDS alerts for 2026-05-21

Affects tlp clearSource CIRCL OSINT Feed

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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 · public exploit available · 85% EPSS : block it and hunt for it in your logs now.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.2Critical
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:X/RC:R

Exploitation evidence

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

  1. Disclosed: evidence found.

    CVE published 13 Jun 2023

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CVSS exploit maturity: proof of concept public

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV the same day as disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Fortinet, Inc.

    , 96 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. Added to CISA KEV (opens in a new tab)

    exploitation confirmed · ransomware use known

    , the same day as disclosure

  4. KEV remediation due

    US federal deadline

    , 21 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Description

This report details IDS alerts from 2026-05-21 indicating reconnaissance activity targeting Fortigate VPN devices. Multiple IP addresses were observed making repeated GET requests to the /remote/logincheck endpoint, associated with CVE-2023-27997, a heap-based buffer overflow vulnerability in Fortinet FortiOS and FortiProxy SSL-VPN. Additional IPs showed suspicious or test user-agent strings, suggesting scanning or probing behavior. No active exploitation or confirmed compromises were reported. The activity is assessed as low severity due to its reconnaissance nature without evidence of exploitation.

Indicators of compromise

IP addresses 13

  • 2001:470:1:fb5::260ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
  • 43.133.66.51ET USER_AGENTS User-Agent (_TEST_)
  • 43.131.23.154ET USER_AGENTS User-Agent (_TEST_)
  • 43.157.98.187ET USER_AGENTS User-Agent (_TEST_)
  • 43.130.26.3ET USER_AGENTS User-Agent (_TEST_)
  • 43.157.191.20ET USER_AGENTS User-Agent (_TEST_)
  • 43.130.101.151ET USER_AGENTS User-Agent (_TEST_)
  • 43.156.232.190ET USER_AGENTS User-Agent (_TEST_)
  • 65.49.1.66ET EXPLOIT Fortigate VPN - Repeated GET Requests to /remote/logincheck (CVE-2023-27997)
  • 43.153.192.98ET USER_AGENTS User-Agent (_TEST_)

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