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CVE-2026-19621— Mattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads

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）以及 11.8.x（≤ 11.8.5）在广播帖子删除 WebSocket 事件或返回线程 API 响应之前，未能从帖子负载中剥离操作集成（action integration）的密钥。该漏洞允许已认证的信道成员通过 WebSocket 事件或线程 REST API，从交互式消息帖子中获取服务器端的 Webhook URL 及认证上下文。Mattermost 安全公告编号：MMSA-20

CVSS 6.5 · Medium EPSS 0.25% · P15

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-2026-19621

Vulnerability Information
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Vulnerability Title
Mattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads
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 strip action integration secrets from post payloads before broadcasting post-deletion web socket events and returning thread API responses, which allows an authenticated channel member to obtain server-side webhook URLs and authentication context from interactive-message posts via the post_deleted websocket event or the threads REST API.. Mattermost Advisory ID: MMSA-2026-00766
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
信息暴露
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-2026-19621

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III. Intelligence Information for CVE-2026-19621

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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-2026-16251 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-2026-18256 4.3 MEDIUM Private team metadata disclosure via the team search API
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-200

V. Comments for CVE-2026-19621

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