Security readout for executives and security teams
Plain-English summary
CVE-2021-26090 is a Fortinet FortiMail Webmail memory handling flaw. An unauthenticated remote attacker could send specially crafted login requests that consume available memory, potentially degrading mail service availability. The provided sources describe availability impact only, not data theft or account compromise.
Executive priority
Treat this as a moderate availability risk for affected FortiMail systems, especially internet-facing mail gateways. Prioritize inventory and vendor-guided remediation, but do not frame it as confirmed active exploitation based on the supplied evidence.
Technical view
The vulnerability is a missing release of memory after its effective lifetime in FortiMail Webmail. It affects FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6. CVSS 3.1 is 5.3 with network attack vector, low complexity, no privileges, no user interaction, and low availability impact.
Likely exposure
Exposure is most likely where affected FortiMail Webmail login interfaces are reachable from untrusted networks. Organizations using FortiMail outside the listed versions are not shown as affected in the supplied bundle. Internet-facing deployments deserve priority review because the flaw requires no authentication.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. The described attack condition is unauthenticated remote access to Webmail login handling, but the sources do not provide exploit prevalence, public exploit maturity, or incident evidence.
Researcher notes
The supplied data supports a denial-of-service style memory exhaustion issue in Webmail login handling. No CWE is listed, and no exploit details, fixed versions, or active exploitation evidence are included in the bundle. Avoid assuming broader Fortinet product impact beyond FortiMail versions named here.
Mitigation direction
- Identify all FortiMail deployments and their exact software versions.
- Check Fortinet advisory FG-IR-21-042 for vendor-approved fixed releases or mitigations.
- Apply Fortinet-supported updates according to change-control requirements.
- Restrict Webmail login exposure to trusted networks where operationally feasible.
- Monitor FortiMail memory usage and service availability for abnormal pressure.
Validation and detection
- Compare deployed FortiMail versions against 6.4.0-6.4.4 and 6.2.0-6.2.6.
- Confirm whether Webmail login is reachable from the internet or untrusted networks.
- Review monitoring for unexplained memory exhaustion or service degradation.
- Verify remediation status against Fortinet advisory FG-IR-21-042.
- Document compensating controls if immediate upgrade is not possible.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2021-26090 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
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://fortiguard.com/advisory/FG-IR-21-042CVE 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.