What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2022-01-10
• EPSS: 33.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-05-29 · updated 2026-06-17
• Weakness: CWE-787

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.

Affected products

• Fortinet FortiOS (FortiGate): from 5.2.0 before 5.2.15; from 5.4.0 before 5.4.13; from 5.6.0 before 5.6.11; from 6.0.0 before 6.0.5 — fixed in 5.2.15, 5.4.13, 5.6.11, 6.0.5
• Fortinet FortiProxy: before 1.2.9; 2.0.0 — fixed in 1.2.9

How to fix

Upgrade to a fixed version: Fortinet FortiOS (FortiGate) 5.2.15, 5.4.13, 5.6.11, 6.0.5; Fortinet FortiProxy 1.2.9. Check the vendor advisory for mitigations.

References

• https://fortiguard.com/advisory/FG-IR-18-388
• https://fortiguard.com/advisory/FG-IR-20-229
• https://fortiguard.com/advisory/FG-IR-18-388
• https://fortiguard.com/advisory/FG-IR-20-229
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-13383

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