Signal is active with 2 mentions in latest observed window
Recommended action window: Monitor and triage in normal cycle
NVD description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
Priority
LOW
Exploitation
NONE
PoC
NONE
Patch
NONE
Momentum
NONE
If you run products in this scope, you should treat this CVE as relevant to your environment.
CVE-2026-4265 Mattermost Guest User Privilege Escalation via Unauthorized File Upload Metadata https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-4265
Post summary
The post announces CVE‑2026‑4265, a guest‑user privilege escalation flaw in Mattermost triggered by unauthorized file upload metadata, but it does not provide exploit code, mitigation steps, or evidence of active exploitation.
CVE-2026-4265 Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post fil… https://www.cve.org/CVERecord?id=CVE-2026-4265
Post summary
The statement discloses that CVE-2026-4265 impacts specific Mattermost releases, exposing a permission validation flaw that permits guest users to upload files.
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| Part | Vendor | Product | Version | Target SW | Target HW |
|---|---|---|---|---|---|
| App | mattermost | mattermost_server | - | - | - |