Security readout for executives and security teams
Plain-English summary
Mattermost Server versions before 4.2.0, 4.1.1, and 4.0.5 had a phishing-related issue where an error page could include a link. The public record gives limited detail and no CVSS score, so urgency depends on whether affected Mattermost instances are still running.
Executive priority
Treat this as a targeted hygiene issue, not a confirmed active exploitation emergency. Patch any legacy Mattermost deployments and verify unsupported versions are not internet-facing.
Technical view
CVE-2017-18891 is described as a Mattermost Server phishing issue affecting releases before 4.2.0, 4.1.1, and 4.0.5. The available source bundle does not provide CWE, CVSS, proof-of-exploitation, or detailed attack mechanics.
Likely exposure
Exposure is limited to organizations running Mattermost Server versions older than 4.2.0, 4.1.1, or 4.0.5. The bundled affected-products metadata is incomplete, listing vendor and product as n/a.
Exploitation context
The source bundle does not indicate active exploitation, and CISA KEV status is false. Public details only state that an error page can have a link, enabling phishing risk.
Researcher notes
Evidence is sparse: no CVSS, CWE, affected CPEs, exploit status, or detailed technical root cause are present in the supplied record. Avoid assuming scope beyond Mattermost Server before the fixed versions named.
Mitigation direction
- Upgrade Mattermost Server to 4.2.0, 4.1.1, 4.0.5, or a later supported release.
- Review Mattermost security updates for any branch-specific remediation guidance.
- Prioritize externally accessible Mattermost instances during remediation.
- If upgrade timing is constrained, follow vendor guidance and reduce exposure where feasible.
Validation and detection
- Inventory all Mattermost Server instances and record exact versions.
- Confirm no production instance runs a version before 4.2.0, 4.1.1, or 4.0.5.
- Review externally exposed Mattermost deployments first.
- Check internal phishing reports for Mattermost-linked error page themes.
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-2017-18891 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.