CVE-2026-95666Unbounded post ID array in the bulk reactions endpoint allows denial of service
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No exploitation reported and no EPSS estimate yet.
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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
- CVSS
- 4.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Mattermost
- NVD analysis
- Analyzed
- Record last updated
- Sep 22, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Mattermost Mattermost mattermost:mattermost (from the name) | from 11.9.0 through 11.9.1; from 11.8.0 through 11.8.5; from 11.7.0 through 11.7.10; from 11.10.0 through 11.10.1; 11.11.0 not affected; 11.9.2 not affected; 11.8.6 not affected; 11.7.11 not affected; and 1 more ranges | CNA record |
mattermost mattermost_server mattermost:mattermost_server | from 11.7.0 before 11.7.11; from 11.8.0 before 11.8.6; from 11.9.0 before 11.9.2; from 11.10.0 before 11.10.2 | NVD |
References
- https://mattermost.com/security-updatesvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.