Security readout for executives and security teams
Plain-English summary
FortiMail versions before 7.0.0 had a flaw in its Identity-Based Encryption service. If an attacker could intercept encrypted messages, they may be able to tamper with them and recover plaintext. The issue is not listed as actively exploited in CISA KEV, and the CVSS attack complexity is high.
Executive priority
Handle as a moderate confidentiality risk. It warrants remediation for organizations relying on FortiMail encrypted messaging, but the available sources do not show active exploitation or broad product impact.
Technical view
CVE-2021-26100 is a missing cryptographic step in Fortinet FortiMail before 7.0.0. The CVSS 3.1 vector is AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating unauthenticated network exposure, high attack complexity, and high confidentiality impact without integrity or availability impact in the CVSS scoring.
Likely exposure
Exposure is limited to Fortinet FortiMail deployments before 7.0.0 using the Identity-Based Encryption service, especially where encrypted messages could be intercepted in transit. The source bundle does not identify other Fortinet products or unaffected branches.
Exploitation context
The cited CVE data describes a network attacker who intercepts encrypted messages and manipulates them to enable tampering and plaintext recovery. CISA KEV status is false in the bundle, and no source here claims public exploitation.
Researcher notes
Evidence is narrow but consistent: affected product is Fortinet FortiMail before 7.0.0, with impact tied to the IBE service and intercepted encrypted messages. Do not broaden scope beyond FortiMail or claim exploitation without additional evidence.
Mitigation direction
- Identify FortiMail systems running versions before 7.0.0.
- Upgrade impacted FortiMail systems to 7.0.0 or later where applicable.
- Review Fortinet advisory FG-IR-21-003 for vendor-specific guidance.
- Prioritize systems using the Identity-Based Encryption service.
- Treat potentially exposed encrypted message content as sensitive until assessed.
Validation and detection
- Confirm deployed FortiMail version on every appliance or instance.
- Verify whether the Identity-Based Encryption service is enabled or used.
- Review mail security logs for unusual encrypted-message handling.
- Check whether encrypted messages traversed untrusted networks.
- Document upgrade status against Fortinet advisory FG-IR-21-003.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2021-26100 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://fortiguard.com/advisory/FG-IR-21-003CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.