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CVE-2021-36166

32
FAUCET Score

CVE-2021-36166 is an improper authentication vulnerability affecting FortiMail versions prior to 7.0.1, allowing a remote attacker to efficiently guess an administrative account's authentication token. This vulnerability carries a critical CVSS score of 9.8, indicating a high impact on confidentiality, integrity, and availability, with a low attack complexity and no user interaction required. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), it has garnered significant community discussion with 10 mentions, suggesting awareness among security professionals.

Impacted Technologies

VendorProductVersion(s)CPE
<= 5.4.12CPE matchmatch criteria
cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:*
>= 6.0.0, < 6.0.12CPE matchmatch criteria
cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:*
>= 6.2.0, < 6.2.8CPE matchmatch criteria
cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:*
>= 6.4.0, < 6.4.6CPE matchmatch criteria
cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:*
7.0.0CPE matchmatch criteria
cpe:2.3:a:fortinet:fortimail:7.0.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.47%
Probability of exploitation in next 30 days
EPSS Percentile
71.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0147 is in the 58th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

fortinetvendor investigatingvia nvd_reference
View patch

References

fortiguard.com / psirt/FG-IR-21-028
Vendor Advisory