How severe is CVE-2021-26100?

CVE-2021-26100 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-26100 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26100?

CVE-2021-26100 affects Fortinet Fortimail. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-26100?

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

When was CVE-2021-26100 published?

CVE-2021-26100 was published on 2021-07-09 and last updated on 2026-06-17.

CVE-2021-26100

CVE-2021-26100 is a medium-severity vulnerability in Fortinet Fortimail with a CVSS 3.x base score of 5.9. 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-347.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
CVSS v2: 5.0
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-347
Affected product: Fortinet Fortimail
Published: 2021-07-09
Last modified: 2026-06-17

Description

A missing cryptographic step in the Identity-Based Encryption service of FortiMail before 7.0.0 may allow an unauthenticated attacker who intercepts the encrypted messages to manipulate them in such a way that makes the tampering and the recovery of the plaintexts possible.

Frequently asked questions

What is CVE-2021-26100?: A missing cryptographic step in the Identity-Based Encryption service of FortiMail before 7.0.0 may allow an unauthenticated attacker who intercepts the encrypted messages to manipulate them in such a way that makes the tampering and the recovery of the plaintexts possible.
How severe is CVE-2021-26100?: CVE-2021-26100 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-26100 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26100?: CVE-2021-26100 affects Fortinet Fortimail. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-26100?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-26100 published?: CVE-2021-26100 was published on 2021-07-09 and last updated on 2026-06-17.

References

https://fortiguard.com/advisory/FG-IR-21-003

Affected products (1)

cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:*

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