Security readout for executives and security teams
Plain-English summary
Mattermost Server had a SAML login flaw that could let an attacker sign in as another user using a crafted SAML response. This is an account-takeover risk, especially for organizations using SAML-based single sign-on.
Executive priority
Treat this as high priority where Mattermost uses SAML, because the impact is account takeover. Urgency is lower for non-SAML deployments, but version verification should still be completed.
Technical view
CVE-2018-21263 affects Mattermost Server before 4.7.0, 4.6.2, and 4.5.2. The described issue is improper handling of a crafted SAML response, allowing authentication to a different user's account. No CVSS, CWE, or detailed affected CPE data is provided.
Likely exposure
Likely exposure is Mattermost Server deployments older than 4.7.0, 4.6.2, or 4.5.2 that use SAML authentication. The source bundle does not identify CPEs or additional affected product variants.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. Exploitability is described at a vulnerability level only: an attacker could authenticate as another user through a crafted SAML response.
Researcher notes
Evidence is limited to the CVE description and Mattermost security update reference. There is no CVSS vector, CWE mapping, CPE list, exploit status, or detailed root-cause data in the provided bundle.
Mitigation direction
- Upgrade Mattermost Server to 4.7.0, 4.6.2, 4.5.2, or a later supported release.
- Review Mattermost security updates for version-specific guidance.
- Prioritize remediation on deployments using SAML SSO.
- Review authentication logs for unusual cross-account access patterns.
Validation and detection
- Inventory Mattermost Server versions across production and internal deployments.
- Confirm whether SAML authentication is enabled on each deployment.
- Verify upgraded instances report fixed or later versions.
- Review login records for unexpected user switches or anomalous SAML sign-ins.
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-2018-21263 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.