Security readout for executives and security teams
Plain-English summary
Mattermost Server failed to enforce the expiration time on SAML login responses before versions 4.7.0, 4.6.2, and 4.5.2. For organizations using SAML single sign-on, this could weaken login assurance. The public sources do not provide CVSS, CWE, exploit details, or confirmed active exploitation.
Executive priority
Prioritize remediation for Mattermost instances using SAML SSO, especially internet-accessible or business-critical collaboration systems. Severity is not quantified in the sources, so urgency should be driven by SAML use, exposure, and upgrade feasibility.
Technical view
The flaw is in Mattermost Server SAML response validation: affected versions did not enforce the SAML response expiration date. Fixed version thresholds are 4.7.0, 4.6.2, and 4.5.2. Available source data does not define impact scope beyond this behavior or provide exploitability scoring.
Likely exposure
Exposure is most likely in Mattermost Server deployments older than 4.7.0, 4.6.2, or 4.5.2 that use SAML authentication. Deployments not using SAML are less clearly exposed based on the provided sources.
Exploitation context
No provided source reports active exploitation, and the CVE is not marked in KEV. The weakness concerns acceptance of expired SAML responses, but the public bundle does not include exploit prerequisites, observed attacks, or proof-of-concept status.
Researcher notes
The source record is sparse: no CVSS, CWE, affected CPEs, or exploit references are provided. Analysis should stay focused on SAML response expiration enforcement and fixed Mattermost version thresholds unless additional vendor advisories are obtained.
Mitigation direction
- Upgrade Mattermost Server to 4.7.0, 4.6.2, 4.5.2, or a later supported release.
- Use Mattermost security updates as the authoritative remediation reference.
- Prioritize SAML-enabled Mattermost environments during remediation planning.
- If upgrade timing is uncertain, check current Mattermost vendor guidance before applying compensating controls.
Validation and detection
- Inventory Mattermost Server versions across production and non-production environments.
- Confirm whether each Mattermost deployment has SAML authentication enabled.
- Verify upgraded systems are at or above the fixed version threshold.
- Review authentication logs for unusual SAML login patterns around the exposure window.
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-2018-21264 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
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://mattermost.com/security-updates/CVE 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.