CVE-2026-18560

Improper order of authorisations in Mattermost GetFile API leads to an authenticated user to determine a post’s quarantined status

State: Published
Severity: 4.3 Medium
Published: Oct 16, 2026
Updated: Oct 16, 2026
Reserved: Aug 1, 2026

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Description

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate user’s permissions before other validations which allows non-content reviewers to infer a post’s flagged status via direct API call.. Mattermost Advisory ID: MMSA-2026-00754

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N	Mattermost

Weaknesses

CWE-203 Observable Discrepancy

Affected Products

Product	Versions
MattermostMattermost	11.10.0 through 11.10.0Affected 11.7.0 through 11.7.9Affected 11.9.0 through 11.9.1Affected 11.8.0 through 11.8.5Affected 11.11.0Not affected 11.10.1Not affected 11.7.10Not affected 11.9.2Not affected 11.8.6Not affected

References

MMSA-2026-00754vendor-advisory

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