Security readout for executives and security teams
Plain-English summary
CVE-2018-21260 is a privacy flaw in older Mattermost Server releases. During some user-management activity, WebSocket events were sent when they should not have been, potentially exposing user-related information to unintended recipients.
Executive priority
Schedule remediation through normal security patching, with higher priority where Mattermost handles sensitive teams, executives, customers, or regulated communications.
Technical view
Mattermost Server emitted WebSocket events during certain user-management operations, violating user privacy. The CVE does not describe code execution, privilege escalation, or authentication bypass. The affected range is described as Mattermost Server before 4.8.1, 4.7.4, and 4.6.3.
Likely exposure
Organizations running Mattermost Server older than 4.8.1, 4.7.4, or 4.6.3 may be exposed. The source bundle does not identify affected editions, configurations, or the exact user-management operations involved.
Exploitation context
The provided sources do not report active exploitation, public exploitation, or CISA KEV inclusion. Treat this as a privacy exposure issue unless additional vendor or incident evidence shows misuse.
Researcher notes
Evidence is sparse: no CVSS, CWE, detailed affected matrix, or exploit details are provided. The reliable facts are the product, fixed version thresholds, WebSocket event privacy impact, and lack of KEV signal.
Mitigation direction
- Upgrade Mattermost Server to 4.8.1, 4.7.4, 4.6.3, or a later supported release.
- Review Mattermost security updates for version-specific vendor guidance.
- Prioritize upgrades on internet-accessible or broadly used internal Mattermost deployments.
- Apply normal change control and verify service compatibility before production rollout.
Validation and detection
- Inventory Mattermost Server versions across production and non-production environments.
- Confirm no deployed instance is older than 4.8.1, 4.7.4, or 4.6.3.
- Review user-management audit logs for unusual administrative activity during exposure windows.
- Check vendor advisories for any added details not present in the CVE bundle.
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-2018-21260 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.