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CVE-2026-18256

Private team metadata disclosure via the team search API

Medium4.3EPSS 0.16%
Published
Updated
Reserved
Assigned by
Mattermost

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 properly restrict private teams from public team search results, which allows an authenticated user without permission to list private teams to disclose the ID, name, and display name of private teams via a modified team search request. Mattermost Advisory ID: MMSA-2026-00748

Scores

CVSS scores of CVE-2026-18256, by who scored it
Scored byCVSSScoreVector
MattermostCNA (assigner)3.1Medium4.3CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
NVDNVD · Analyzed3.1Medium4.3CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
EPSS (exploitation in 30 days)
0.16% · top 95% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.3.

Weakness

Affected products

  • Mattermost · Mattermost

    • affected 11.10.0 – ≤ 11.10.0
    • affected 11.7.0 – ≤ 11.7.9
    • affected 11.9.0 – ≤ 11.9.1
    • affected 11.8.0 – ≤ 11.8.5
    • unaffected 11.11.0
    • unaffected 11.10.1
    • unaffected 11.7.10
    • unaffected 11.9.2
    • unaffected 11.8.6

What to do

Solution: Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

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Record last updated .