Security readout for executives and security teams
Plain-English summary
A malformed link posted in a Mattermost channel can make vulnerable Mattermost Server versions hang. The business impact is loss of collaboration availability, not proven data theft or code execution. Public sources name fixed release branches but provide limited technical detail.
Executive priority
Treat as a moderate availability risk. Remediate during normal vulnerability maintenance unless Mattermost is mission-critical or broadly accessible, then accelerate the upgrade.
Technical view
Mattermost Server before 4.10.1, 4.9.4, and 4.8.2 is affected by a denial-of-service condition triggered by a malformed link in a channel. Sources do not provide CVSS, CWE, authentication requirements, or exploit detail.
Likely exposure
Organizations running Mattermost Server versions earlier than 4.10.1, 4.9.4, or 4.8.2 may be exposed, especially where users can post channel links.
Exploitation context
The provided sources do not report active exploitation, and this CVE is not marked as KEV. The described impact is application hang through malformed channel content.
Researcher notes
Evidence is sparse: the public description identifies affected versions and DoS impact, but omits root cause, CVSS, CWE, and preconditions. Avoid inferring exploitability beyond malformed channel links.
Mitigation direction
- Upgrade Mattermost Server to 4.10.1, 4.9.4, 4.8.2, or later supported releases.
- Review Mattermost security updates for branch-specific upgrade guidance.
- Prioritize externally accessible or business-critical Mattermost deployments.
- Do not rely on unverified workarounds as primary remediation.
Validation and detection
- Inventory Mattermost Server versions across production and non-production environments.
- Confirm vulnerable instances are below 4.10.1, 4.9.4, or 4.8.2.
- Verify upgraded systems report a fixed or later version.
- Review incident logs for unexplained Mattermost hangs around channel link activity.
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-2018-21259 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.