CVE-2026-4055Network attack vector

Cross-team run creation via mismatched permission check

Published May 21, 2026 · Updated May 21, 2026

Incorrect authorization in Mattermost 11.5.0 through 11.5.1 allows remote authenticated users to create Playbook runs in other teams. The run creation API accepts a caller-supplied team ID but checks run_create against the caller's current team rather than the target team. Ordinary team membership is sufficient, and the bounded impact is unauthorized cross-team Playbook run creation without reported data disclosure or service interruption.

CVSS severity4.3
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Mattermost 11.5.0 through 11.5.1 allows remote authenticated users to create Playbook runs in other teams. The run creation API accepts a caller-supplied team ID but checks run_create against the caller's current team rather than the target team. Ordinary team membership is sufficient, and the bounded impact is unauthorized cross-team Playbook run creation without reported data disclosure or service interruption.

The record

CVE
CVE-2026-4055
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-863
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 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?

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  1. Affected versionversion=11.5.0 <=11.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=11.5.0 <=11.5.1

Published CVSS scores

4.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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