---
id: "CVE-2018-13383"
kind: "vulnerability"
aliases: ["CVE-2018-13383"]
title: "Fortinet FortiOS and FortiProxy: Fortinet FortiOS and FortiProxy Out-of-bounds Write"
severity: "medium"
cvss: 6.5
epss: 0.33647
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Fortinet FortiOS and FortiProxy", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "fortinet", "fortios", "fortiproxy", "infrastructure", "ransomware", "ssl-vpn"]
not_affected_if: ["non-fortinet-gateway", "ssl-vpn-disabled"]
published_at: "2019-05-29T18:29:00+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-13383", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2018-13383", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2018-13383", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Fortinet FortiOS and FortiProxy: Fortinet FortiOS and FortiProxy Out-of-bounds Write

A heap buffer overflow in Fortinet FortiOS and FortiProxy's SSL VPN web service can crash the service for logged-in users. The sources tie it to ransomware use and in-the-wild exploitation, but do not confirm code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Fortinet FortiOS and FortiProxy affected ? fixed ?

## Fix

Apply the Fortinet update for FortiOS and FortiProxy per vendor instructions; the sources do not name the fixed version.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-13383
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2018-13383
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2018-13383

## From the sources

A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_