CVE-2026-4055

Insufficient permission validation on cross-team playbook run creation

MEDIUM

4.3

CVSS Score

Published: May 21, 2026 at 07:13 AM UTC

Updated: July 23, 2026 at 07:32 PM UTC

2 products affected across 1 vendorMattermost ServerMattermost

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Severity

MEDIUM4.3

Exploit prediction

EPSS 0.2%

SSVC

No known exploit

Description

Mattermost versions 11.5.x <= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629

Affected

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

Mattermost Server · Mattermost

95%

10.11.0 ≤ v < 10.11.1711.5.0 ≤ v < 11.5.511.6.0 ≤ v < 11.6.2

Affected range stops below 10.11.17, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.5.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 11.6.2, so it looks safe — our inference, not a vendor statement

Mattermost · Mattermost

60%

11.5.0 ≤ v ≤ 11.5.111.5.0

Vendor states this is fixed in 10.11.14 (unaffected)

Vendor states this is fixed in 11.4.4 (unaffected)

Vendor states this is fixed in 11.5.2 (unaffected)

Vendor states this is fixed in 11.6.0 (unaffected)

Remediation

No guide yet

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

Patch and advisory references

https://mattermost.com/security-updates

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: LOW
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-863

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