CVE-2023-27997
A critical heap‑based buffer overflow exists in FortiOS and FortiProxy firmware that can be triggered by specially crafted SSL‑VPN requests. The flaw allows a remote attacker to run arbitrary code on the device. It affects many older FortiOS and FortiProxy versions.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
FortiOS versions 7.2.4 and earlier, 7.0.11 and earlier, 6.4.12 and earlier, 6.0.16 and earlier; FortiProxy versions 7.2.3 and earlier, 7.0.9 and earlier, 2.0.12 and earlier, 1.2 and 1.1 all versions; also FortiGate 6000 and 7000 series.
Real-world impact
An attacker who can reach the device over the network could send a crafted SSL‑VPN packet and gain full control, allowing them to execute commands, install malware, or take the device offline.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability is exploitable remotely without authentication, has no user interaction, and gives the attacker complete control over confidentiality, integrity, and availability.
What to do about it
- 01Apply the latest FortiOS or FortiProxy update as per vendor instructions.
CISA KEV required action
Timeline
- Jun 13, 2023 · Jun 13, 2023Confirmed exploited (CISA KEV)CISA added it to the Known Exploited Vulnerabilities catalog — attackers are using it in the wild.
- Jun 13, 2023 · Jun 13, 2023PublishedDisclosed and added to the National Vulnerability Database.
- Jul 4, 2023 · Jul 4, 2023CISA remediation deadlineFederal agencies are required to remediate by this date.
- Jul 31, 2026 · 6d agoAdvisory updatedThe NVD record was last revised.
- Jul 31, 2026 · 6d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
How it’s attacked
References & advisories
- fortiguard.com/psirt/FG-IR-23-097vendor advisory
- cisa.gov/known-exploited-vulnerabili…us government resource