CVE-2026-93851 — Path traversal in Mattermost Agents plugin mention reminder allows plugin replacement via crafted post
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 fail to validate the target post ID in the Agents plugin's mention reminder component, which allows an authenticated user who can post in a channel visible to a system administrator to cause the administrator's browser to send an unintended API request, resulting in replacement of an installed plugin and code execution on the server, via a crafted post containing a forged mention reminder that the administrator clicks. Mattermost Advisory ID: MMSA-2026-00742
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Mattermost Mattermost).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- Search available logs for exploit probes matching the vulnerability class (file handling), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Mattermost | Mattermost | ≥ 11.9.0 and ≤ 11.9.1≥ 11.8.0 and ≤ 11.8.5≥ 11.7.0 and ≤ 11.7.10 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.0 | CVSS 3.1 | High | 1.3 | 6.0 | responsibledisclosure@mattermost.com via NIST National Vulnerability Database |
| 8.0 | CVSS 3.1 | High | — | — | Mattermost via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H (score shown at the top: responsibledisclosure@mattermost.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Monitor file creation in web directories and paths with traversal sequences (../).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · mattermost/mattermost
- Record published
- CVSS changed · 8.0
- Source status changed · → Received
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 28, 2026 – Oct 28, 2026
- 1× Official description updated · Oct 28, 2026 – Oct 28, 2026
References
1 on the record
Elsewhere on this site
Related CVEs (same products)
- Low CVE-2026-93846 Team admin can escalate a team member's permissions via the team member roles endpoint 2d
- Low CVE-2026-93847 Improper post type validation on scheduled post endpoints 2d
- Low CVE-2026-93848 Mattermost OpenID discovery endpoint request bypasses outbound connection filtering, allowing SSRF by a System Administrator 2d
- Medium CVE-2026-93850 Unbounded memory consumption during PDF text extraction 2d
- Medium CVE-2026-93849 Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames 2d
- Medium CVE-2026-116516 Insufficient length validation when parsing Zoom chat transcriptions 2d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-93851 is "Path traversal in Mattermost Agents plugin mention reminder allows plugin replacement via crafted post", rated High. It affects Mattermost (Mattermost); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.0 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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