# CVE-2018-13383: Fortinet FortiOS and FortiProxy Out-of-bounds Write

Source: https://junglewise.ai/threats/cve-2018-13383-fortinet-fortios-and-fortiproxy-out-of-bounds-write  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2022-01-10. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2018-13383 · Severity: critical · CVSS 6.5 · Exploited in the wild · Published 2022-01-10

A heap buffer overflow vulnerability in the SSL VPN web portal of Fortinet FortiOS and FortiProxy occurs when proxying webpages due to improper handling of JavaScript href data. This flaw can allow a remote attacker to cause the termination of the SSL VPN web service for logged-in users.

Technologies: [Fortinet FortiOS](https://junglewise.ai/threats/technologies/fortios), [Fortinet FortiProxy](https://junglewise.ai/threats/technologies/fortiproxy). Vendors: [Fortinet](https://junglewise.ai/threats/vendors/fortinet).

## Quick answers

**Is CVE-2018-13383 exploited in the wild?** Yes. CVE-2018-13383 is known to be exploited in the wild, first recorded on 10 January 2022. Treat it as urgent.

**How severe is CVE-2018-13383?** Critical severity, with a CVSS score of 6.5, published 10 January 2022.

**Which products and versions are affected?** 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; Fortinet FortiProxy 2.0.0, 1.2.8 and earlier.

**Is there a fix for CVE-2018-13383?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2018-13383 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2018-13383?** Check whether you run Fortinet FortiOS or Fortinet FortiProxy. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- 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
- Fortinet FortiProxy 2.0.0, 1.2.8 and earlier

## Timeline

- 2022-01-10: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2022-01-10: disclosed
- 2022-01-10: exploited: Reported as exploited in the wild per CISA KEV and advisory metadata.

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- [Fortinet FortiOS authentication bypass in HA command execution](https://junglewise.ai/threats/cve-2026-126259-a-missing-authentication-for-critical-function-vulnerability-in)
- [Fortinet FortiOS stack buffer overflow in WAD proxy](https://junglewise.ai/threats/cve-2026-126258-a-stack-based-buffer-overflow-vulnerability-in-fortinet-fortios)
- [Fortinet FortiOS out-of-bounds read in kernel](https://junglewise.ai/threats/cve-2026-126256-a-out-of-bounds-read-vulnerability-in-fortinet-fortios-8-0-0)
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- [Fortinet FortiOS numeric truncation error in BGP daemon](https://junglewise.ai/threats/cve-2026-126254-a-numeric-truncation-error-vulnerability-in-fortinet-fortios-8-0)