Mattermost 9.0
Mattermost 9.0
The Mattermost 9.0 reached end of service life on Dec 15, 2023 — 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 9.0 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
- 9.0
- product Label
- Mattermost
- release Label
- 9.0
- codename
- lts
- latest Version
- 9.0.5
- release Date
- 2023-09-14
- maintained
- source Url
- https://endoflife.date/mattermost
Lifecycle Dates
- End of Service Life
- Dec 15, 2023
- Last OEM Support
- Dec 15, 2023
OEM vs. 3rd Party Support
See how third-party support compares to the vendor contract for Mattermost 9.0 — 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 9.0?
Vulnerability Remediation
Scanning, mitigation and patch-around guidance for Mattermost 9.0 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 9.0 Support: Frequently Asked Questions
Is the Mattermost 9.0 still supported?
Mattermost ended support for the Mattermost 9.0 on Dec 15, 2023 — 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 9.0 end of service life (EOSL) date?
Mattermost lists the end of service life for the Mattermost 9.0 as Dec 15, 2023.
Can I keep using the Mattermost 9.0 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 9.0 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 9.0
17 published CVEs affect the Mattermost 9.0, including 2 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-2023-45316 | HIGH | 7.3 | Dec 12, 2023 | Mattermost fails to validate if a relative path is passed in /plugins/playbooks/api/v0/telemetry/run/<telem_run_id> as a telemetry run ID, allowing an attacker to use a path traversal payload that points to a different endpoint leading to a CSRF attack. |
| CVE-2023-6458 | HIGH | 7.1 | Dec 6, 2023 | Mattermost webapp fails to validate route parameters in/<TEAM_NAME>/channels/<CHANNEL_NAME> allowing an attacker to perform a client-side 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-2023-46701 | MEDIUM | 6.5 | Dec 12, 2023 | Mattermost fails to perform authorization checks in the /plugins/playbooks/api/v0/runs/add-to-timeline-dialog endpoint of the Playbooks plugin allowing an attacker to get limited information about a post if they know the post ID |
| CVE-2025-27936 | MEDIUM | 5.3 | Apr 16, 2025 | Mattermost Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison. |
| CVE-2026-2461 | MEDIUM | 4.3 | Mar 16, 2026 | Mattermost Plugins versions <=11.3 11.0.3 11.2.2 10.10.11.0 fail to implement authorisation checks on comment block modifications, which allows an authorised attacker with editor permission to modify comments created by other board members. Mattermost Advisory ID: MMSA-2025-00559 |
| CVE-2025-11776 | MEDIUM | 4.3 | Nov 14, 2025 | Mattermost versions <11 fail to properly restrict access to archived channel search API which allows guest users to discover archived public channels via the `/api/v4/teams/{team_id}/channels/search_archived` endpoint |
| CVE-2024-24988 | MEDIUM | 4.3 | Feb 29, 2024 | Mattermost fails to properly validate the length of the emoji value in the custom user status, allowing an attacker to send multiple times a very long string as an emoji value causing high resource consumption and possibly crashing the server. |
| CVE-2024-23493 | MEDIUM | 4.3 | Feb 29, 2024 | Mattermost fails to properly authorize the requests fetching team associated AD/LDAP groups, allowing a user to fetch details of AD/LDAP groups of a team that they are not a member of. |
| CVE-2024-1402 | MEDIUM | 4.3 | Feb 9, 2024 | Mattermost fails to check if a custom emoji reaction exists when sending it to a post and to limit the amount of custom emojis allowed to be added in a post, allowing an attacker sending a huge amount of non-existent custom emojis in a post to crash the mobile app of a user seeing the post and to crash the server due to overloading when clients attempt to retrive the aforementioned post. |
| CVE-2023-47858 | MEDIUM | 4.3 | Jan 2, 2024 | Mattermost fails to properly verify the permissions needed for viewing archived public channels, allowing a member of one team to get details about the archived public channels of another team via the GET /api/v4/teams/<team-id>/channels/deleted endpoint. |
| CVE-2023-49874 | MEDIUM | 4.3 | Dec 12, 2023 | Mattermost fails to check whether a user is a guest when updating the tasks of a private playbook run allowing a guest to update the tasks of a private playbook run if they know the run ID. |
| CVE-2023-49809 | MEDIUM | 4.3 | Dec 12, 2023 | Mattermost fails to handle a null request body in the /add endpoint, allowing a simple member to send a request with null request body to that endpoint and make it crash. After a few repetitions, the plugin is disabled. |
| CVE-2023-49607 | MEDIUM | 4.3 | Dec 12, 2023 | Mattermost fails to validate the type of the "reminder" body request parameter allowing an attacker to crash the Playbook Plugin when updating the status dialog. |
| CVE-2023-45847 | MEDIUM | 4.3 | Dec 12, 2023 | Mattermost fails to to check the length when setting the title in a run checklist in Playbooks, allowing an attacker to send a specially crafted request and crash the Playbooks plugin |
| CVE-2025-41436 | LOW | 3.1 | Nov 14, 2025 | Mattermost versions <11.0 fail to properly enforce the "Allow users to view archived channels" setting which allows regular users to access archived channel content and files via the "Open in Channel" functionality from followed threads |
| CVE-2024-23488 | LOW | 3.1 | Feb 29, 2024 | Mattermost fails to properly restrict the access of files attached to posts in an archived channel, resulting in members being able to access files of archived channels even if the “Allow users to view archived channels” option is disabled. |