Security readout for executives and security teams
Plain-English summary
Older Mattermost Server releases allowed an attacker to make fake posts that appeared to be system messages. This could mislead users or administrators inside a collaboration platform, damaging trust and supporting phishing or operational confusion. The provided sources do not report data theft, code execution, or active exploitation.
Executive priority
Treat this as a moderate integrity and trust issue for Mattermost environments. Prioritize remediation if Mattermost is used for incident response, operations, executive communications, or customer support workflows.
Technical view
Mattermost Server before 4.3.0, 4.2.1, and 4.1.2 allowed fictive system-message posts through webhooks and slash commands using the v3 or v4 REST API. The source bundle provides no CVSS score, CWE, authentication detail, or exploit status.
Likely exposure
Exposure is likely limited to Mattermost Server deployments older than 4.3.0, 4.2.1, or 4.1.2. Risk is higher where webhooks, slash commands, or REST API access are enabled and reachable by users or integrations.
Exploitation context
The bundle does not show CISA KEV listing or cited active exploitation. The described issue is message-forgery and trust abuse inside Mattermost, not confirmed remote code execution or direct data compromise.
Researcher notes
Public detail in the provided bundle is sparse. Focus validation on version confirmation, integration permissions, and whether webhooks or slash commands can create misleading system-style messages. Avoid assuming prerequisites or impact beyond the cited description.
Mitigation direction
- Upgrade Mattermost Server to 4.3.0, 4.2.1, 4.1.2, or later as appropriate.
- Review Mattermost security updates for vendor-specific remediation guidance.
- Restrict webhook and slash command access to trusted users and integrations.
- Audit integrations that can post to channels through REST APIs.
Validation and detection
- Inventory Mattermost Server versions across production and non-production systems.
- Confirm no deployment is older than 4.3.0, 4.2.1, or 4.1.2.
- Review enabled webhooks and slash commands for unnecessary or stale integrations.
- Check channel history and audit logs for unexpected system-message style posts.
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-2017-18889 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.