CVE-2026-95666Network attack vectorHinoki check available

Authenticated denial of service via unbounded post IDs

Published Sep 22, 2026 · Updated Sep 22, 2026

Resource exhaustion in affected Mattermost releases allows remote authenticated users to overload the database through crafted requests. The bulk reactions endpoint accepts a POST /api/v4/posts/ids/reactions request containing an unbounded post-ID array and sends the oversized workload to the database. An account is required; affected versions are 11.7.0 through 11.7.10, 11.8.0 through 11.8.5, 11.9.0 through 11.9.1, and 11.10.0 through 11.10.1, and the resulting load can interrupt service.

CVSS severityUnavailable
Unscored
EPSS probability0.37%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Resource exhaustion in affected Mattermost releases allows remote authenticated users to overload the database through crafted requests. The bulk reactions endpoint accepts a POST /api/v4/posts/ids/reactions request containing an unbounded post-ID array and sends the oversized workload to the database. An account is required; affected versions are 11.7.0 through 11.7.10, 11.8.0 through 11.8.5, 11.9.0 through 11.9.1, and 11.10.0 through 11.10.1, and the resulting load can interrupt service.

The record

CVE
CVE-2026-95666
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=11.10.0 <=11.10.1
  2. Affected versionversion=11.7.0 <=11.7.10
  3. Affected versionversion=11.8.0 <=11.8.5
  4. Affected versionversion=11.9.0 <=11.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=11.10.0 <=11.10.1; version=11.7.0 <=11.7.10; version=11.8.0 <=11.8.5; version=11.9.0 <=11.9.1

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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