vulntracker.iovulntracker.io
© 2026 vulntracker.io

CVE-2026-95666

Unbounded post ID array in the bulk reactions endpoint allows denial of service

MEDIUM
4.3
CVSS Score
Published: September 22, 2026 at 01:11 PM UTC
Updated: October 7, 2026 at 04:48 PM UTC
2 products affected across 1 vendorMattermost ServerMattermost

Using Mattermost by Mattermost?

Get instant alerts when new vulnerabilities affect Mattermost - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Start FreeSign In
Severity
MEDIUM4.3
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mattermost Server· Mattermost
95%
11.10.0 ≤ v < 11.10.211.7.0 ≤ v < 11.7.1111.8.0 ≤ v < 11.8.611.9.0 ≤ v < 11.9.2
Affected range stops below 11.10.2, so it looks safe — our inference, not a vendor statement
Affected range stops below 11.7.11, so it looks safe — our inference, not a vendor statement
Affected range stops below 11.8.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 11.9.2, so it looks safe — our inference, not a vendor statement
Mattermost· Mattermost
60%
11.10.0 ≤ v ≤ 11.10.111.7.0 ≤ v ≤ 11.7.1011.8.0 ≤ v ≤ 11.8.511.9.0 ≤ v ≤ 11.9.111.10.011.7.011.8.011.9.0
Vendor states this is fixed in 11.10.2 (unaffected)
Vendor states this is fixed in 11.11.0 (unaffected)
Vendor states this is fixed in 11.7.11 (unaffected)
Vendor states this is fixed in 11.8.6 (unaffected)
Vendor states this is fixed in 11.9.2 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (1)

Vendor Advisory
Source: cverecord
https://mattermost.com/security-updates

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.3MEDIUMMattermost
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Vector?

Quick Info

StatusANALYZED
CWE
CWE-770

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create accountSign in
Free plan, no card