Security readout for executives and security teams
Plain-English summary
This issue can let an attacker make a vulnerable Mattermost Server consume excessive CPU, potentially disrupting team messaging availability. The public record identifies Mattermost Server before 5.15.0 and describes denial of service through an APIv4 request path. No active exploitation is cited in the provided sources.
Executive priority
Treat as a timely availability risk if Mattermost is business-critical or internet-facing. Prioritize upgrading unsupported or pre-5.15.0 deployments, but current evidence does not justify emergency critical handling without additional exposure indicators.
Technical view
CVE-2019-20858 is a denial-of-service flaw in Mattermost Server before 5.15.0. Crafted characters in a SQL LIKE clause reaching an APIv4 endpoint can cause CPU consumption. The bundle does not provide CVSS, CWE, authentication requirements, or precise endpoint details.
Likely exposure
Exposure is likely limited to Mattermost Server deployments running versions before 5.15.0, especially where APIv4 endpoints are reachable by untrusted users. Authentication requirements are not stated in the provided sources.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The known impact is availability loss through CPU exhaustion, not confirmed data theft or code execution.
Researcher notes
Public detail is sparse: no CVSS vector, CWE, auth requirement, or exact endpoint is included. Keep validation non-disruptive and source-grounded. Use version inventory, exposure review, logs, and vendor advisories rather than attempting production reproduction.
Mitigation direction
- Upgrade Mattermost Server versions older than 5.15.0 after reviewing vendor guidance.
- Check Mattermost security updates for the applicable fixed release and operational notes.
- Reduce untrusted access to Mattermost API endpoints where business requirements allow.
- Monitor Mattermost CPU saturation and API request anomalies until remediation is complete.
Validation and detection
- Inventory Mattermost Server versions and identify any instance older than 5.15.0.
- Confirm whether APIv4 endpoints are exposed to untrusted networks or users.
- Review monitoring for unexplained Mattermost CPU spikes or availability degradation.
- Verify upgraded instances report version 5.15.0 or later.
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-2019-20858 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.