How severe is CVE-2021-36188?

CVE-2021-36188 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-36188 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36188?

CVE-2021-36188 affects Fortinet Fortiweb. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-36188?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-36188 published?

CVE-2021-36188 was published on 2021-12-08 and last updated on 2026-06-17.

CVE-2021-36188

CVE-2021-36188 is a medium-severity vulnerability in Fortinet Fortiweb with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (47th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Fortinet Fortiweb
Published: 2021-12-08
Last modified: 2026-06-17

Description

A improper neutralization of input during web page generation ('cross-site scripting') in Fortinet FortiWeb version 6.4.1 and below, 6.3.15 and below allows attacker to execute unauthorized code or commands via crafted GET parameters in requests to login and error handlers

Frequently asked questions

What is CVE-2021-36188?: A improper neutralization of input during web page generation ('cross-site scripting') in Fortinet FortiWeb version 6.4.1 and below, 6.3.15 and below allows attacker to execute unauthorized code or commands via crafted GET parameters in requests to login and error handlers
How severe is CVE-2021-36188?: CVE-2021-36188 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-36188 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36188?: CVE-2021-36188 affects Fortinet Fortiweb. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-36188?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-36188 published?: CVE-2021-36188 was published on 2021-12-08 and last updated on 2026-06-17.

References

https://fortiguard.com/advisory/FG-IR-21-118

Affected products (1)

cpe:2.3:a:fortinet:fortiweb:*:*:*:*:*:*:*:*

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