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CVE-2026-96260

Mattermost server missing request body size limit on plugin routes allows denial of service by an authenticated user

MEDIUM
6.5
CVSS Score
Published: September 22, 2026 at 08:34 PM UTC
Updated: October 7, 2026 at 04:37 PM UTC
2 products affected across 1 vendorMattermost ServerMattermost

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Severity
MEDIUM6.5
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 enforce a request body size limit during CSRF validation of plugin requests which allows an authenticated user to exhaust server memory and cause a denial of service via a large request body sent to a plugin endpoint.. Mattermost Advisory ID: MMSA-2026-00775

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

6.5MEDIUMMattermost
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-789

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