Mattermost 9.11 (ESR)
Mattermost 9.11 (ESR)
The Mattermost 9.11 (ESR) reached end of service life on May 15, 2025 — Mattermost no longer ships security patches or fixes for it. Our third-party support keeps it safe to run: 24/7 engineers manage issues, remediate vulnerabilities, and help you maintain compliance.
24/7 engineers own your Mattermost 9.11 (ESR) incidents end to end.
Mitigation and patch-around guidance when the vendor no longer ships fixes.
Controls evidence and documentation that keep auditors satisfied.
Specifications
- product
- mattermost
- release
- 9.11
- product Label
- Mattermost
- release Label
- 9.11 (ESR)
- codename
- lts
- true
- latest Version
- 9.11.18
- release Date
- 2024-08-02
- maintained
- source Url
- https://endoflife.date/mattermost
Lifecycle Dates
- End of Service Life
- May 15, 2025
- Last OEM Support
- May 15, 2025
OEM vs. 3rd Party Support
See how third-party support compares to the vendor contract for Mattermost 9.11 (ESR) — monitoring, break/fix, vulnerability work, operations and compliance, before and after EOSL.
| Feature | OEM Support | 3rd Party Support |
|---|---|---|
| Post-EOSL Support | ||
| Break/Fix Support | Until EOSL | |
| 24/7 Monitoring | ||
| Vulnerability Scanning & Remediation | ||
| Managed Operations | ||
| Procedure & Configuration Review | ||
| Compliance & Audit Documentation | Limited | |
| Discounted Migration to Other Platforms |
Why Choose 3rd Party Support for Mattermost 9.11 (ESR)?
Vulnerability Remediation
Scanning, mitigation and patch-around guidance for Mattermost 9.11 (ESR) when the vendor no longer ships fixes.
Compliance Maintenance
Procedure review, controls evidence and the documentation auditors ask for — maintained continuously, not scrambled at audit time.
24/7 Expert Support
Engineers who know this release monitor, manage and fix issues around the clock — break/fix to managed operations.
Mattermost 9.11 (ESR) Support: Frequently Asked Questions
Is the Mattermost 9.11 (ESR) still supported?
Mattermost ended support for the Mattermost 9.11 (ESR) on May 15, 2025 — no more patches or fixes from the vendor. Third-party support keeps it covered: our engineers manage issues, remediate vulnerabilities, and help you maintain compliance for as long as you run it.
When is the Mattermost 9.11 (ESR) end of service life (EOSL) date?
Mattermost lists the end of service life for the Mattermost 9.11 (ESR) as May 15, 2025.
Can I keep using the Mattermost 9.11 (ESR) after its EOSL date?
Yes. EOSL means Mattermost stops issuing patches and support — the software itself keeps running. Third-party support covers it from there: issue management, security vulnerability remediation, and the compliance documentation auditors ask for, for as long as you choose to run it.
How much does third-party support for the Mattermost 9.11 (ESR) cost?
Typically 40-70% below the OEM maintenance renewal price. Exact pricing depends on quantity, service level and location — request a quote and we respond within 24 hours.
Known Vulnerabilities Affecting Mattermost 9.11 (ESR)
76 published CVEs affect the Mattermost 9.11 (ESR), including 7 rated critical or high severity. Mattermost no longer ships security patches for this release — our engineers provide mitigation guidance, workarounds and hardening support.
| CVE | Severity | CVSS | Published | Summary |
|---|---|---|---|---|
| CVE-2025-4981 | CRITICAL | 9.9 | Jun 20, 2025 | Mattermost versions 10.5.x <= 10.5.5, 9.11.x <= 9.11.15, 10.8.x <= 10.8.0, 10.7.x <= 10.7.2, 10.6.x <= 10.6.5 fail to sanitize filenames in the archive extractor which allows authenticated users to write files to arbitrary locations on the filesystem via uploading archives with path traversal sequences in filenames, potentially leading to remote code execution. The vulnerability impacts instances where file uploads and document search by content is enabled (FileSettings.EnableFileAttachments = t |
| CVE-2025-25279 | CRITICAL | 9.9 | Feb 24, 2025 | Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate board blocks when importing boards which allows an attacker could read any arbitrary file on the system via importing and exporting a specially crafted import archive in Boards. |
| CVE-2025-20051 | CRITICAL | 9.9 | Feb 24, 2025 | Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate input when patching and duplicating a board, which allows a user to read any arbitrary file on the system via duplicating a specially crafted block in Boards. |
| CVE-2025-24490 | CRITICAL | 9.6 | Feb 24, 2025 | Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to use prepared statements in the SQL query of boards reordering which allows an attacker to retrieve data from the database, via a SQL injection when reordering specially crafted boards categories. |
| CVE-2024-11599 | HIGH | 8.2 | Nov 28, 2024 | Mattermost versions 10.0.x <= 10.0.1, 10.1.x <= 10.1.1, 9.11.x <= 9.11.3, 9.5.x <= 9.5.11 fail to properly validate email addresses which allows an unauthenticated user to bypass email domain restrictions via carefully crafted input on email registration. |
| CVE-2025-9079 | HIGH | 8.0 | Sep 19, 2025 | Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.1, 10.9.x <= 10.9.3 fail to validate import directory path configuration which allows admin users to execute arbitrary code via malicious plugin upload to prepackaged plugins directory |
| CVE-2025-25068 | HIGH | 7.5 | Mar 21, 2025 | Mattermost versions 10.4.x <= 10.4.2, 10.3.x <= 10.3.3, 9.11.x <= 9.11.8, 10.5.x <= 10.5.0 fail to enforce MFA on plugin endpoints, which allows authenticated attackers to bypass MFA protections via API requests to plugin-specific routes. |
| CVE-2025-8023 | MEDIUM | 6.8 | Aug 21, 2025 | Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2 fails to sanitize path traversal sequences in template file destination paths, which allows a system admin to perform path traversal attacks via malicious path components, potentially enabling malicious file placement outside intended directories. |
| CVE-2025-49222 | MEDIUM | 6.8 | Aug 21, 2025 | Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2, 10.10.x <= 10.10.0 fail to validate upload types in remote cluster upload sessions which allows a system admin to upload non-attachment file types via shared channels that could potentially be placed in arbitrary filesystem directories. |
| CVE-2025-36530 | MEDIUM | 6.8 | Aug 21, 2025 | Mattermost versions 10.9.x <= 10.9.1, 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate file paths during plugin import operations which allows restricted admin users to install unauthorized custom plugins via path traversal in the import functionality, bypassing plugin signature enforcement and marketplace restrictions. |
| CVE-2025-6233 | MEDIUM | 6.8 | Jul 18, 2025 | Mattermost versions 10.8.x <= 10.8.1, 10.7.x <= 10.7.3, 10.5.x <= 10.5.7, 9.11.x <= 9.11.16 fail to sanitize input paths of file attachments in the bulk import JSONL file, which allows a system admin to read arbitrary system files via path traversal. |
| CVE-2025-55070 | MEDIUM | 6.5 | Nov 14, 2025 | Mattermost versions <11 fail to enforce multi-factor authentication on WebSocket connections which allows unauthenticated users to access sensitive information via WebSocket events |
| CVE-2025-6226 | MEDIUM | 6.5 | Jul 18, 2025 | Mattermost versions 10.5.x <= 10.5.6, 10.8.x <= 10.8.1, 10.7.x <= 10.7.3, 9.11.x <= 9.11.16 fail to verify authorization when retrieving cached posts by PendingPostID which allows an authenticated user to read posts in private channels they don't have access to via guessing the PendingPostID of recently created posts. |
| CVE-2025-41395 | MEDIUM | 6.5 | Apr 24, 2025 | Mattermost versions 10.4.x <= 10.4.2, 10.5.x <= 10.5.0, 9.11.x <= 9.11.10 fail to properly validate the props used by the RetrospectivePost custom post type in the Playbooks plugin, which allows an attacker to create a specially crafted post with maliciously crafted props and cause a denial of service (DoS) of the web app for all users. |
| CVE-2025-35965 | MEDIUM | 6.5 | Apr 24, 2025 | Mattermost versions 10.4.x <= 10.4.2, 10.5.x <= 10.5.0, 9.11.x <= 9.11.10 fail to validate the uniqueness and quantity of task actions within the UpdateRunTaskActions GraphQL operation, which allows an attacker to create task items containing an excessive number of actions triggered by specific posts, overloading the server and leading to a denial-of-service (DoS) condition. |
| CVE-2025-20621 | MEDIUM | 6.5 | Jan 16, 2025 | Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly handle posts with attachments containing fields that cannot be cast to a String, which allows an attacker to cause the webapp to crash via creating and sending such a post to a channel. |
| CVE-2025-20088 | MEDIUM | 6.5 | Jan 15, 2025 | Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post props which allows a malicious authenticated user to cause a crash via a malicious post. |
| CVE-2025-20086 | MEDIUM | 6.5 | Jan 15, 2025 | Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post props which allows a malicious authenticated user to cause a crash via a malicious post. |
| CVE-2025-21088 | MEDIUM | 6.5 | Jan 15, 2025 | Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate the style of proto supplied to an action's style in post.props.attachments, which allows an attacker to crash the frontend via crafted malicious input. |
| CVE-2024-54682 | MEDIUM | 6.5 | Dec 16, 2024 | Mattermost versions 10.1.x <= 10.1.2, 10.0.x <= 10.0.2, 9.11.x <= 9.11.4, 9.5.x <= 9.5.12 fail to limit the file size for slack import file uploads which allows a user to cause a DoS via zip bomb by importing data in a team they are a team admin. |
Showing the 20 most severe of 76 known CVEs.
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