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779 vulnerabilities found for mattermost by mattermost
CVE-2026-4915 (GCVE-0-2026-4915)
Vulnerability from cvelistv5 – Published: 2026-05-25 07:10 – Updated: 2026-05-25 07:10
VLAI
Title
Server panic via outgoing webhook responses
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
Severity
6.5 (Medium)
CWE
- CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
Credits
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CVE-2026-28735 (GCVE-0-2026-28735)
Vulnerability from cvelistv5 – Published: 2026-05-22 16:26 – Updated: 2026-05-22 16:56
VLAI
Title
GitHub OAuth Scope Validation
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628
Severity
5.4 (Medium)
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
Credits
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CVE-2026-4635 (GCVE-0-2026-4635)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:28 – Updated: 2026-05-22 12:06
VLAI
Title
Persistent notification timing attack causing server denial of service
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637
Severity
6.5 (Medium)
CWE
- CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
Credits
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CVE-2026-3473 (GCVE-0-2026-3473)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:27 – Updated: 2026-05-22 12:12
VLAI
Title
Improper file ownership validation in the Boards API allows unauthorised file access
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620
Severity
5.9 (Medium)
CWE
- CWE-639 - Authorization Bypass Through User-Controlled Key
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
Credits
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CVE-2026-4646 (GCVE-0-2026-4646)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:25 – Updated: 2026-05-22 12:13
VLAI
Title
Insufficient input validation in GitHub plugin API causes denial of service
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID: MMSA-2026-00638
Severity
4.3 (Medium)
CWE
- CWE-1287 - Improper Validation of Specified Type of Input
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-3636 (GCVE-0-2026-3636)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:23 – Updated: 2026-05-22 12:13
VLAI
Title
Sanitize team member data returned by API
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to sanitize team member data when returned via API to users without elevated permissions which allows a user without permissions to get data about team members roles via invoking various team API endpoints.. Mattermost Advisory ID: MMSA-2026-00626
Severity
4.3 (Medium)
CWE
- CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
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Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-5740 (GCVE-0-2026-5740)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:22 – Updated: 2026-05-22 12:14
VLAI
Title
Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647
Severity
7.5 (High)
CWE
- CWE-789 - Memory Allocation with Excessive Size Value
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-5308 (GCVE-0-2026-5308)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:20 – Updated: 2026-05-22 12:14
VLAI
Title
Missing request body size limits on Zoom plugin HTTP endpoints
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to enforce request body size limits on plugin HTTP endpoints which allows an attacker to cause a denial of service via crafted oversized HTTP requests.. Mattermost Advisory ID: MMSA-2026-00646
Severity
4.9 (Medium)
CWE
- CWE-400 - Uncontrolled Resource Consumption
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-5755 (GCVE-0-2026-5755)
Vulnerability from cvelistv5 – Published: 2026-05-22 10:18 – Updated: 2026-05-22 12:15
VLAI
Title
Denial of service via crafted TIFF file upload
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.2, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the TIFF IFD offset in the image header before allocating memory, which allows authenticated users with file upload or posting permissions to cause a denial of service (server OOM) via uploading a crafted TIFF file or posting a URL that serves one.. Mattermost Advisory ID: MMSA-2026-00648
Severity
6.5 (Medium)
CWE
- CWE-400 - Uncontrolled Resource Consumption
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.2 (semver) Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.3 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-22880 (GCVE-0-2026-22880)
Vulnerability from cvelistv5 – Published: 2026-05-21 08:22 – Updated: 2026-05-21 12:39
VLAI
Title
Mobile SSO authentication flow allows credential theft via malicious server
Summary
Mattermost Mobile Apps versions <=2.37 11.4 2.0.37 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to properly validate the SSO authentication callback origin which allows an attacker controlling a malicious Mattermost server to steal user credentials for a legitimate Mattermost server via relaying the SSO code exchange flow through the mobile application. Mattermost Advisory ID: MMSA-2025-00564
Severity
6.1 (Medium)
CWE
- CWE-352 - Cross-Site Request Forgery (CSRF)
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 2.0.37
(semver)
Affected: 0 , ≤ 11.0.4 (semver) Affected: 0 , ≤ 11.1.3 (semver) Affected: 0 , ≤ 11.3.2 (semver) Affected: 0 , ≤ 10.11.11 (semver) Unaffected: 2.38.0 Unaffected: 11.5.0 Unaffected: 2.37.1.0 Unaffected: 11.4.1 Unaffected: 11.3.2 Unaffected: 11.2.4 Unaffected: 10.11.12 |
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CVE-2026-4858 (GCVE-0-2026-4858)
Vulnerability from cvelistv5 – Published: 2026-05-21 08:12 – Updated: 2026-05-22 03:55
VLAI
Title
Path traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to check integration URL for path traversal which allows an malicious authenticated user to call an arbitrary API via system admin Mattermost auth token using via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640
Severity
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-4055 (GCVE-0-2026-4055)
Vulnerability from cvelistv5 – Published: 2026-05-21 07:13 – Updated: 2026-05-21 12:39
VLAI
Title
Insufficient permission validation on cross-team playbook run creation
Summary
Mattermost versions 11.5.x <= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629
Severity
4.3 (Medium)
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-3471 (GCVE-0-2026-3471)
Vulnerability from cvelistv5 – Published: 2026-05-18 08:45 – Updated: 2026-05-18 14:35
VLAI
Title
Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App
Summary
Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618
Severity
6.5 (Medium)
CWE
- CWE-939 - Improper Authorization in Handler for Custom URL Scheme
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 6.0.1
(semver)
Affected: 0 , ≤ 5.4.13 (semver) Unaffected: 6.2.0 Unaffected: 6.1.1.0 Unaffected: 5.13.5.0 |
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CVE-2026-4643 (GCVE-0-2026-4643)
Vulnerability from cvelistv5 – Published: 2026-05-18 08:43 – Updated: 2026-05-18 14:36
VLAI
Title
Calling window.close() from server-side content causes crash in the Mattermost Desktop App
Summary
Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent server-rendered content from closing an underlying application view in the Mattermost Desktop App which allows a malicious server or plugin to crash the desktop client via invoking {{window.close()}} in the renderer context, leading to a denial of service condition at the client level. Mattermost Advisory ID: MMSA-2026-00633
Severity
CWE
- CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 6.0.1
(semver)
Affected: 0 , ≤ 5.4.13 (semver) Unaffected: 6.2.0 Unaffected: 6.1.1.0 Unaffected: 5.13.5.0 |
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CVE-2026-6333 (GCVE-0-2026-6333)
Vulnerability from cvelistv5 – Published: 2026-05-18 08:41 – Updated: 2026-05-19 17:19
VLAI
Title
SSRF via Host Header Spoofing in Custom Slash Commands
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
Severity
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 |
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CVE-2026-4858 (GCVE-0-2026-4858)
Vulnerability from nvd – Published: 2026-05-21 08:12 – Updated: 2026-05-22 03:55
VLAI
Title
Path traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.
Summary
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to check integration URL for path traversal which allows an malicious authenticated user to call an arbitrary API via system admin Mattermost auth token using via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640
Severity
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.6.0 , ≤ 11.6.0
(semver)
Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15 |
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CVE-2026-22880 (GCVE-0-2026-22880)
Vulnerability from nvd – Published: 2026-05-21 08:22 – Updated: 2026-05-21 12:39
VLAI
Title
Mobile SSO authentication flow allows credential theft via malicious server
Summary
Mattermost Mobile Apps versions <=2.37 11.4 2.0.37 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to properly validate the SSO authentication callback origin which allows an attacker controlling a malicious Mattermost server to steal user credentials for a legitimate Mattermost server via relaying the SSO code exchange flow through the mobile application. Mattermost Advisory ID: MMSA-2025-00564
Severity
6.1 (Medium)
CWE
- CWE-352 - Cross-Site Request Forgery (CSRF)
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 2.0.37
(semver)
Affected: 0 , ≤ 11.0.4 (semver) Affected: 0 , ≤ 11.1.3 (semver) Affected: 0 , ≤ 11.3.2 (semver) Affected: 0 , ≤ 10.11.11 (semver) Unaffected: 2.38.0 Unaffected: 11.5.0 Unaffected: 2.37.1.0 Unaffected: 11.4.1 Unaffected: 11.3.2 Unaffected: 11.2.4 Unaffected: 10.11.12 |
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CVE-2026-4055 (GCVE-0-2026-4055)
Vulnerability from nvd – Published: 2026-05-21 07:13 – Updated: 2026-05-21 12:39
VLAI
Title
Insufficient permission validation on cross-team playbook run creation
Summary
Mattermost versions 11.5.x <= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629
Severity
4.3 (Medium)
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-6347 (GCVE-0-2026-6347)
Vulnerability from nvd – Published: 2026-05-18 08:30 – Updated: 2026-05-18 14:38
VLAI
Title
Mattermost Calls plugin exposes TURN server credentials in plaintext in support packets
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields in the Mattermost Calls plugin which allows an attacker with access to a support packet to obtain TURN server credentials via the plaintext values present in the exported plugin configuration.. Mattermost Advisory ID: MMSA-2026-00605
Severity
7.6 (High)
CWE
- CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-6346 (GCVE-0-2026-6346)
Vulnerability from nvd – Published: 2026-05-18 08:37 – Updated: 2026-05-18 14:37
VLAI
Title
Sensitive credentials exposed in plaintext in Mattermost support packets
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields before including them in support packet generation, which allows a Mattermost System Admin or any party with access to a support packet to obtain sensitive credentials in plaintext via downloading a support packet from the System Console.. Mattermost Advisory ID: MMSA-2026-00607
Severity
8.7 (High)
CWE
- CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-6345 (GCVE-0-2026-6345)
Vulnerability from nvd – Published: 2026-05-18 08:40 – Updated: 2026-05-19 03:55
VLAI
Title
Prevent password disclosure and force reset during Slack import
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail prevent disclosure of created user password which allows a malicious attacker to impersonate a user via the use of some of those passwords.. Mattermost Advisory ID: MMSA-2026-00614
Severity
6.5 (Medium)
CWE
- CWE-522 - Insufficiently Protected Credentials
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-6343 (GCVE-0-2026-6343)
Vulnerability from nvd – Published: 2026-05-18 08:32 – Updated: 2026-05-18 14:37
VLAI
Title
Mattermost Playbooks Plugin fails to enforce view permissions in list endpoints, allowing unauthorized access to public playbooks
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check public/private permissions which allows members without these permissions to access public playbooks via /get.. Mattermost Advisory ID: MMSA-2026-00591
Severity
4.3 (Medium)
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-6339 (GCVE-0-2026-6339)
Vulnerability from nvd – Published: 2026-05-18 08:05 – Updated: 2026-05-18 12:42
VLAI
Title
Missing request origin validation on burn-on-read reveal endpoint
Summary
Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost Advisory ID: MMSA-2026-00636
Severity
4.3 (Medium)
CWE
- CWE-346 - Origin Validation Error
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 11.4.4 |
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CVE-2026-6333 (GCVE-0-2026-6333)
Vulnerability from nvd – Published: 2026-05-18 08:41 – Updated: 2026-05-19 17:19
VLAI
Title
SSRF via Host Header Spoofing in Custom Slash Commands
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
Severity
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 |
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CVE-2026-5163 (GCVE-0-2026-5163)
Vulnerability from nvd – Published: 2026-05-18 08:11 – Updated: 2026-05-18 14:40
VLAI
Title
Missing authorization check in AI message rewrite endpoint allows access to private thread content
Summary
Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645
Severity
6.5 (Medium)
CWE
- CWE-862 - Missing Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Unaffected: 11.6.0 Unaffected: 11.5.2 |
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CVE-2026-4643 (GCVE-0-2026-4643)
Vulnerability from nvd – Published: 2026-05-18 08:43 – Updated: 2026-05-18 14:36
VLAI
Title
Calling window.close() from server-side content causes crash in the Mattermost Desktop App
Summary
Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent server-rendered content from closing an underlying application view in the Mattermost Desktop App which allows a malicious server or plugin to crash the desktop client via invoking {{window.close()}} in the renderer context, leading to a denial of service condition at the client level. Mattermost Advisory ID: MMSA-2026-00633
Severity
CWE
- CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 6.0.1
(semver)
Affected: 0 , ≤ 5.4.13 (semver) Unaffected: 6.2.0 Unaffected: 6.1.1.0 Unaffected: 5.13.5.0 |
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CVE-2026-4286 (GCVE-0-2026-4286)
Vulnerability from nvd – Published: 2026-05-18 08:07 – Updated: 2026-05-18 12:41
VLAI
Title
Playbooks Plugin fails to validate team transfers, allowing unauthorized removal of member access via playbook update
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to check if {{team_id}} was being changed when updating playbooks, allowing users with only {{Manage Playbook Configurations}} permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID: MMSA-2025-00552
Severity
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 |
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CVE-2026-3471 (GCVE-0-2026-3471)
Vulnerability from nvd – Published: 2026-05-18 08:45 – Updated: 2026-05-18 14:35
VLAI
Title
Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App
Summary
Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618
Severity
6.5 (Medium)
CWE
- CWE-939 - Improper Authorization in Handler for Custom URL Scheme
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 6.0.1
(semver)
Affected: 0 , ≤ 5.4.13 (semver) Unaffected: 6.2.0 Unaffected: 6.1.1.0 Unaffected: 5.13.5.0 |
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CVE-2026-3117 (GCVE-0-2026-3117)
Vulnerability from nvd – Published: 2026-05-18 08:09 – Updated: 2026-05-18 14:38
VLAI
Title
Instance and webhook GitLab plugin commands were able to be run by non-admin users
Summary
Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the {{gitlab instance {option}}} or the {{/gitlab webhook {option}}} commands. Mattermost Advisory ID: MMSA-2026-00600
Severity
6.5 (Medium)
CWE
- CWE-862 - Missing Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
0 , ≤ 11.1.5
(semver)
Affected: 0 , ≤ 10.13.11 (semver) Affected: 0 , ≤ 11.3.4 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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CVE-2026-28732 (GCVE-0-2026-28732)
Vulnerability from nvd – Published: 2026-05-18 08:35 – Updated: 2026-05-18 14:37
VLAI
Title
Slash command trigger-word update allowed command hijacking
Summary
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate existing system or custom slash commands via editing their own slash command trigger to an already-registered trigger through the command update API. Mattermost Advisory ID: MMSA-2026-00597
Severity
4.3 (Medium)
CWE
- CWE-863 - Incorrect Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 10.11.0 , ≤ 10.11.13 (semver) Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 10.11.14 Unaffected: 11.4.4 |
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