CVE-2021-26091 Weak cryptography in FortiMail

What is CVE-2021-26091?

CVE-2021-26091 is a medium-severity vulnerability in Fortinet FortiMail, published on 24 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A use of a cryptographically weak pseudo-random number generator vulnerability in the authenticator of the Identity Based Encryption service of FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to infer parts of users authentication tokens and reset their credentials.

Weakness: CWE-338

Which versions are affected by CVE-2021-26091?

It affects 1 product.

Products include Fortinet Fortimail.

How do I fix CVE-2021-26091?

No fix has been published for CVE-2021-26091 yet. Limit exposure of the affected software until one is available.

Is CVE-2021-26091 being exploited?

There is no known exploitation of CVE-2021-26091 in the wild and no public exploit code.

Other vulnerabilities in Fortinet FortiMail

• CVE-2026-104286 Fortinet FortiMail Path Traversal Exploited Critical 9.8
• CVE-2021-36166 Auth bypass in Fortinet FortiMail Critical 9.8
• CVE-2021-24007 SQL injection in Fortinet FortiMail Critical 9.8
• CVE-2020-9294 Auth bypass in FortiMail Critical 9.8
• CVE-2023-47539 Auth bypass in FortiMail Critical 9.0

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-pmxq-4hqc-9hr4.