CVE-2023-27997: Fortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability

Vulnerability summary

CVE-2023-27997 is a critical (CVSS 9.8) Heap-based Buffer Overflow vulnerability in Fortinet FortiOS and FortiProxy SSL-VPN. It is known to be exploited: CISA and ENISA list it, first on 13-06-2023. It has been used in ransomware campaigns. EPSS estimates a 85.69% chance of exploitation in the next 30 days, higher than 99.7% of scored vulnerabilities.

Timeline

1. 13-06-2023
   PublishedVulnerability first disclosed.
2. 13-06-2023
   Added to CISA KEVFortinet FortiOS and FortiProxy SSL-VPN Heap-Based Buffer Overflow Vulnerability
3. 04-07-2023
   CISA remediation dueApply updates per vendor instructions.
4. 23-01-2025
   Added to ENISA KEVAdded to the ENISA known exploited vulnerabilities catalog.
5. 31-07-2026
   Last modifiedVulnerability information updated.

Description

A heap-based buffer overflow vulnerability [CWE-122] in FortiOS version 7.2.4 and below, version 7.0.11 and below, version 6.4.12 and below, version 6.0.16 and below and FortiProxy version 7.2.3 and below, version 7.0.9 and below, version 2.0.12 and below, version 1.2 all versions, version 1.1 all versions SSL-VPN may allow a remote attacker to execute arbitrary code or commands via specifically crafted requests.

• CWE-122Heap-based Buffer OverflowA 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().
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.