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CVE-2026-18256— Private team metadata disclosure via the team search API

Quick assessment

Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mattermost 版本 11.10.x（≤ 11.10.0）、11.7.x（≤ 11.7.9）、11.9.x（≤ 11.9.1）和 11.8.x（≤ 11.8.5）未能正确限制将私有团队包含在公共团队搜索结果中。这导致无权限的已认证用户可通过构造修改后的团队搜索请求，泄露私有团队的 ID、名称及显示名称。 Mattermost 安全公告编号：MMSA-2026-00748

CVSS 4.3 · Medium EPSS 0.16% · P5

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 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 affected
11.11.0 unaffected
11.10.1 unaffected
11.7.10 unaffected
11.9.2 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-18256

Vulnerability Information
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Vulnerability Title
Private team metadata disclosure via the team search API
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.10.0 ~ 11.10.0 -

II. Public POCs for CVE-2026-18256

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III. Intelligence Information for CVE-2026-18256

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Same Patch Batch · Mattermost · 2026-10-16 · 15 CVEs total

CVE-2026-16453 7.1 HIGH Mattermost SAML RelayState forgery allows unauthorized team membership
CVE-2026-19541 6.5 MEDIUM Outgoing OAuth connection client secret exposure during connection validation
CVE-2026-18551 6.5 MEDIUM Mattermost guest account privilege escalation via member roles API
CVE-2026-19621 6.5 MEDIUM Mattermost leaks interactive-message integration secrets to non-admin users via post-delet
CVE-2026-16251 6.5 MEDIUM Mattermost local image proxy allows server memory exhaustion via unbounded image response
CVE-2026-18795 6.4 MEDIUM Missing server side validation allowed user to quarantine a DM and GM post
CVE-2026-18223 5.0 MEDIUM Mattermost invitation tokens not bound to invited email address allowing unauthorized team
CVE-2026-19601 4.9 MEDIUM Disclosure of AD/LDAP bind password via Test Connection
CVE-2026-19600 4.5 MEDIUM Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth
CVE-2026-19076 4.4 MEDIUM Mattermost fails to reject OAuth application sessions in account type switch, allowing acc
CVE-2026-19603 4.3 MEDIUM Private channel ID disclosure via user status endpoints
CVE-2026-19867 4.3 MEDIUM Uncapped mention keys in user notification properties allow CPU exhaustion during post pro
CVE-2026-18560 4.3 MEDIUM Improper order of authorisations in Mattermost GetFile API leads to an authenticated user
CVE-2026-18799 4.3 MEDIUM Mattermost Server fails to restrict Slack import account binding, allowing team admins to

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-863

V. Comments for CVE-2026-18256

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