Security readout for executives and security teams
Plain-English summary
This affects Mattermost Server when it is used as an OAuth 2.0 service provider. The documented issue is incorrect handling of a user denial during redirect flow. Business urgency depends on whether Mattermost provides OAuth login or authorization services in your environment.
Executive priority
Prioritize if Mattermost provides OAuth services for users or applications. If Mattermost is not used as an OAuth provider, business urgency is lower but version remediation should still be tracked.
Technical view
CVE-2017-18897 describes a Mattermost Server OAuth 2.0 provider flaw before 4.2.0, 4.1.1, and 4.0.5. The public description says Mattermost mishandles the deny action for a redirection. No CVSS score, CWE, detailed impact, or exploit mechanics are provided in the source bundle.
Likely exposure
Exposure is limited to Mattermost Server deployments using Mattermost as an OAuth 2.0 service provider and running versions before 4.2.0, 4.1.1, or 4.0.5.
Exploitation context
The source bundle does not cite active exploitation, public exploit availability, KEV listing, or exploitation details. Treat exploitation status as unconfirmed.
Researcher notes
Public evidence is sparse: no CVSS, CWE, affected CPEs, or detailed impact are included. Analysis should stay scoped to OAuth provider deny-redirection handling and the fixed Mattermost versions named by the CVE record.
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 branch-specific upgrade guidance.
- Confirm whether Mattermost is configured as an OAuth 2.0 service provider.
- If upgrade timing is uncertain, ask the vendor for supported interim guidance.
Validation and detection
- Inventory Mattermost Server versions across production and non-production systems.
- Check whether OAuth 2.0 service provider functionality is enabled.
- Verify upgraded systems report 4.2.0, 4.1.1, 4.0.5, or later.
- Review authentication logs for unusual OAuth denial or redirect behavior.
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-2017-18897 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.