CVEs / CVE-2018-13383

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

Known exploited in the CISA KEV catalog since 10 Jan 2022
medium 6.5 CVSS 3.1 (NVD)
EPSS 32.4% chance of exploitation in the next 30 days, higher than 98% of CVEs (30 Oct 2026)
Last changed at its sources 17 Jun 2026

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Summary

A heap buffer overflow in Fortinet FortiOS and FortiProxy may cause the SSL VPN web service termination for logged in users.
CISA, Known Exploited Vulnerabilities catalog

Description

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.
The CVE record, via NVD · published 29 May 2019 · NVD status: Analyzed

Affected and fixed versions

As stated by the CVE record (from the CNA)
Product	Affected	Fixed in
Fortinet Fortinet FortiOS and FortiProxy	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, FortiProxy 2.0.0, 1.2.8 and earlier	—

Exploitation

In CISA KEV since	10 Jan 2022
Due date for US federal agencies	10 Jul 2022
Used in ransomware campaigns	Known
Required action	Apply updates per vendor instructions.

Severity

CVSS 3.1	6.5 medium `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H` Scored by NVD
Weakness	CWE-787

References

CVE-2018-13383 on NVD
CVE-2018-13383 in the CISA KEV catalog
https://fortiguard.com/advisory/FG-IR-18-388 Mitigation, Vendor Advisory
https://fortiguard.com/advisory/FG-IR-20-229 Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-13383 US Government Resource

Sources

Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.

This product uses data from the NVD API but is not endorsed or certified by the NVD.