# FortiOS SSL-VPN pre-auth heap overflow (XORtigate, CVE-2023-27997) · pwn.watch

> A heap overflow in the FortiOS and FortiProxy SSL-VPN allowed pre-authentication remote code execution. Fortinet said it may have been exploited in a limited number of cases, and published it alongside its analysis of the Volt Typhoon campaign.

Page: https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997 · generated 2026-10-22T21:08:49.695Z

## Status
- Severity: critical · status: closed · patch: patched
- Product: Fortinet FortiOS and FortiProxy SSL-VPN
- Started: 2023-06-12 · closed: 2023-06-13
- CVEs: CVE-2023-27997
- Affected: FortiOS 7.2.4 and below, 7.0.11 and below, 6.4.12 and below, 6.0.16 and below (NVD); FortiProxy 7.2.3 and below, 7.0.9 and below, 2.0.12 and below, 1.2 and 1.1 all versions (NVD)
- Fixed in: See vendor advisory FG-IR-23-097

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997/feed.xml
- JSON Feed: https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997.json
- This file: https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997/llms.txt

## Updates (newest first)
- 2023-06-13: CISA adds CVE-2023-27997 to the KEV catalog
- 2023-06-12: Fortinet publishes FG-IR-23-097 and a blog post on exploitation and Volt Typhoon (https://www.fortinet.com/blog/psirt-blogs/analysis-of-cve-2023-27997-and-clarifications-on-volt-typhoon-campaign)

## Fix brief
# Security brief: FortiOS SSL-VPN pre-auth heap overflow (XORtigate, CVE-2023-27997)

Source: https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997 · status: closed (closed Jun 13, 2023) · severity: critical · updated Jun 13, 2023

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
A heap overflow in the FortiOS and FortiProxy SSL-VPN allowed pre-authentication remote code execution. Fortinet said it may have been exploited in a limited number of cases, and published it alongside its analysis of the Volt Typhoon campaign.

Severity detail: CVSS 9.8 (NVD), actively exploited (CISA KEV), known ransomware use

- Product: Fortinet FortiOS and FortiProxy SSL-VPN
- CVE / advisory ids: CVE-2023-27997

## Affected versions
- FortiOS 7.2.4 and below, 7.0.11 and below, 6.4.12 and below, 6.0.16 and below (NVD)
- FortiProxy 7.2.3 and below, 7.0.9 and below, 2.0.12 and below, 1.2 and 1.1 all versions (NVD)

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisory FG-IR-23-097

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Jun 13, 2023: CISA adds CVE-2023-27997 to the KEV catalog
- Jun 12, 2023: Fortinet publishes FG-IR-23-097 and a blog post on exploitation and Volt Typhoon

## Advisories
- [FG-IR-23-097: Heap buffer overflow in sslvpn pre-authentication](https://www.fortiguard.com/psirt/FG-IR-23-097) (Fortinet)
- [Analysis of CVE-2023-27997 and Clarifications on Volt Typhoon Campaign](https://www.fortinet.com/blog/psirt-blogs/analysis-of-cve-2023-27997-and-clarifications-on-volt-typhoon-campaign) (Fortinet)
- [NVD: CVE-2023-27997](https://nvd.nist.gov/vuln/detail/CVE-2023-27997) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

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Machine-readable: https://pwn.watch/i/fortinet-fortios-ssl-vpn-xortigate-cve-2023-27997.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.