Security readout for executives and security teams
Plain-English summary
Mattermost Boards could leave a user’s session usable after they log out. If an attacker already has an old session token, logout may not stop access. The issue is medium severity because exploitation requires difficult conditions and user interaction, but confidentiality impact is rated high.
Executive priority
Handle as a targeted confidentiality risk, not an internet-wide emergency. Prioritize environments with sensitive Boards content, shared workstations, weak endpoint controls, or token exposure concerns.
Technical view
CVE-2021-37866 is a CWE-613 session expiration flaw in Mattermost Boards plugin v0.10.0 and earlier. The server does not invalidate a Boards session when the user logs out, allowing authorization with an old session token. Sources do not identify a fixed version, mitigation, or active exploitation.
Likely exposure
Organizations using Mattermost Boards plugin v0.10.0 or earlier are potentially exposed. Risk is most relevant where session tokens may be recoverable from shared devices, logs, backups, browser storage, or compromised endpoints.
Exploitation context
The CVSS vector indicates local attack vector, high complexity, no privileges required, and user interaction required. The source bundle does not show CISA KEV listing or any cited evidence of active exploitation.
Researcher notes
The evidence identifies the vulnerable behavior and affected plugin range but does not provide fixed-version details. Avoid claiming exploitation or prescribing a specific patch without current Mattermost guidance.
Mitigation direction
- Review Mattermost security updates for vendor-confirmed fixed Boards versions.
- Upgrade or replace vulnerable Boards deployments according to vendor guidance.
- If no fix is confirmed, request Mattermost guidance before relying on logout protection.
- Reduce exposure of token-bearing logs, backups, and browser profiles.
Validation and detection
- Inventory Mattermost Boards plugin versions across all Mattermost deployments.
- Flag Boards v0.10.0 and earlier as potentially vulnerable.
- Review session-management assumptions for logout, token expiry, and token revocation.
- Check available Mattermost advisories for a confirmed remediation path.
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.
CWE-613: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-37866 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
- Medium
- CVSS
- 4.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N13.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://mattermost.com/security-updates/CVE reference · x_refsource_MISC
- https://www.whitesourcesoftware.com/vulnerability-database/CVE-2021-37866CVE reference · x_refsource_MISC
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.
Insufficient Session Expiration
Insufficient Session Expiration represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.