Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mattermost | Mattermost | unaffected |
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Project Subscriptions
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Advisories
No advisories yet.
Fixes
Solution
Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher.
Workaround
No workaround given by the vendor.
References
| Link | Providers |
|---|---|
| https://mattermost.com/security-updates |
|
History
Tue, 22 Sep 2026 13:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771 | |
| Title | Unbounded post ID array in the bulk reactions endpoint allows denial of service | |
| Weaknesses | CWE-770 | |
| References |
| |
| Metrics |
cvssV3_1
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Mattermost
Published:
Updated: 2026-09-22T13:11:13.798Z
Reserved: 2026-09-22T13:09:02.237Z
Link: CVE-2026-95666
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
No data.
Weaknesses