What is CVE-2021-26102?

CVE-2021-26102 is a critical-severity vulnerability in Fortinet Fortiwan, classified under Authentication Bypass by Primary Weakness. CVSS score: 9.8/10. Published 2024-12-19.

How severe is CVE-2021-26102?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-26102 known to be exploited?

10 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Path Traversal in Fortinet Fortiwan

CVE-2021-26102

A relative path traversal vulnerability (CWE-23) in FortiWAN version 4.5.7 and below, 4.4 all versions may allow a remote non-authenticated attacker to delete files on the system by sending a crafted POST request. In particular, deleting specific configuration files will reset the Admin password to its default value.

Published 2024-12-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.197 (97.3th percentile), scored 2026-09-28.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 97th percentile — 97.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.168 · newest: 0.197 · change: +0.030

Affected products

Fortinet Fortiwan — versions 4.5.0, 4.4.0

Weakness classification (CWE)

Public proof-of-concept exploits

References

fortiguard.fortinet.com/psirt/FG-IR-21-048 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-26102?: CVE-2021-26102 is a critical-severity vulnerability in Fortinet Fortiwan, classified under Authentication Bypass by Primary Weakness. CVSS score: 9.8/10. Published 2024-12-19.
How severe is CVE-2021-26102?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-26102 known to be exploited?: 10 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.