CVE-2021-24020
A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.62%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of signature verification.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.62% probability · 49th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Affected
- fortinet/fortimail
- Source
- psirt@fortinet.com
EPSS 0.6% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://fortiguard.com/advisory/FG-IR-21-027Vendor Advisory
- https://fortiguard.com/advisory/FG-IR-21-027Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.