FortimailApplication · Fortinet
CVE-2021-26100
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceFortiMail before 7.0.0 has a missing cryptographic step in its Identity-Based Encryption (IBE) service that allows unauthenticated attackers who intercept encrypted messages to manipulate them and recover plaintexts. The vulnerability stems from inadequate integrity verification or authentication in the IBE implementation, enabling man-in-the-middle attacks on encrypted email traffic.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FortimailApplication
< 7.0.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Determine FortiMail versionLog into FortiMail CLI and run the command: get system status. Alternatively, check the web interface under Dashboard > Status, or System > Settings > General > Administration. Locate the Firmware/Version field.Affected if The displayed version number is lower than 7.0.0 (for example, 6.4.x, 6.3.x, or earlier)
-
Verify IBE service is enabledIn FortiMail CLI, run: config ibe setting, then run: show. Alternatively, in the web interface navigate to IBE > IBE Settings. Look for the IBE service status or whether the IBE section is configured.Affected if The IBE service shows as enabled or any IBE policies/keys are configured (the vulnerability only applies when IBE is active)
-
Check IBE encryption settingsIn FortiMail CLI under config ibe setting, verify if integrity verification or authentication parameters are present. Look for options related to message integrity or digital signatures on IBE-protected messages.Affected if No explicit integrity verification or authentication settings are found for IBE-encrypted messages, indicating the vulnerable configuration
You are affected if your FortiMail version is below 7.0.0 AND the Identity-Based Encryption (IBE) service is enabled or configured on your appliance.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data7.0.0
Upgrade FortiMail to version 7.0.0 or later to obtain the patched IBE implementation with proper cryptographic integrity checks.
Fix this in Fortimail
Scoped from the published advisory
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26100 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-26100 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data