Is CVE-2018-13383 being actively exploited?

Yes. CVE-2018-13383 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on January 10, 2022.

What is the CVSS score for CVE-2018-13383?

CVE-2018-13383 has a CVSS 3.1 base score of 4.3 (MEDIUM).

CVE-2018-13383

MEDIUM · CVSS 4.3CISA KEV: actively exploitedEPSS 33.6%EU EUVD: exploited

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.

Key facts

CVSS score: 4.3 (v3.1)
Severity: MEDIUM
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-787
EPSS score: 33.6% (98th percentile)
In CISA KEV: Yes, added January 10, 2022
In EU EUVD: Yes (EUVD-2018-5327)
Published: May 29, 2019
NVD last modified: June 17, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Fortinet FortiOS and FortiProxy Out-of-bounds Write

Added to the KEV catalog on January 10, 2022; federal remediation due July 10, 2022. Known to be used in ransomware campaigns.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2018-5327 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on October 21, 2025.

View on the EU Vulnerability Database

Affected products

fortinet / fortios
fortinet / fortiproxy
fortinet / fortiproxy

Certified products that may be affected

4 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

FortiOS 5.6 - Fortinet, Inc. - FIPS 140 3639 - historical
FortiProxy-400E/2000E/4000E - Fortinet, Inc. - FIPS 140 3628 - historical
Fortinet FortiProxy v1.0 - Fortinet, Inc. - Common Criteria 383-4-475 - archived
FortiOS 5.2 - Fortinet, Inc. - FIPS 140 2765 - historical

References

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)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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