Security readout for executives and security teams
Plain-English summary
Older Mattermost Server releases could be forced to consume excessive memory when handling images with crafted dimensions. The business impact is availability: affected collaboration servers may slow down or become unavailable. The source bundle does not provide CVSS scoring, proof of active exploitation, or detailed workaround guidance.
Executive priority
Treat this as a practical availability risk for affected Mattermost collaboration systems. It does not currently carry evidence of active exploitation in the provided sources, but unpatched exposed servers should be upgraded because denial-of-service impact can disrupt internal communications.
Technical view
CVE-2018-21250 affects Mattermost Server before 5.2.2, 5.1.2, and 4.10.4. The issue is a remotely triggerable denial of service through memory consumption caused by crafted image dimensions. Public source data does not name a CWE, authentication requirement, exploit maturity, or complete affected-version matrix beyond those fixed-version boundaries.
Likely exposure
Exposure is most likely in self-hosted Mattermost Server deployments older than 5.2.2, 5.1.2, or 4.10.4 that accept or process user-supplied images. The source bundle does not identify specific editions, configurations, or hosting models beyond Mattermost Server.
Exploitation context
The CVE description says remote attackers can cause denial of service through crafted image dimensions. CISA KEV status is false in the bundle, and no cited source states active exploitation. Evidence is limited to vulnerability description and vendor security-update reference.
Researcher notes
The public record is sparse: no CVSS vector, CWE, exploit status, or detailed root-cause analysis is included. Analysis should stay bounded to remote memory-consumption denial of service through crafted image dimensions and the stated Mattermost Server fixed-version thresholds.
Mitigation direction
- Upgrade affected Mattermost Server branches to 5.2.2, 5.1.2, 4.10.4, or later applicable releases.
- Review Mattermost security updates for any branch-specific upgrade guidance.
- Prioritize internet-facing or heavily used collaboration servers first.
- Monitor memory consumption and availability until patched.
- If immediate upgrade is impossible, check vendor guidance for supported temporary controls.
Validation and detection
- Inventory all Mattermost Server deployments and record exact versions.
- Confirm no production instance runs below 5.2.2, 5.1.2, or 4.10.4 branch fixes.
- Review whether image upload or image processing paths are reachable by untrusted users.
- Check operational telemetry for unusual memory spikes linked to image handling.
- Verify upgrade completion through version reporting and post-upgrade service health checks.
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-2018-21250 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.