CVE-2026-4915— Server panic via outgoing webhook responses
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是美国Mattermost公司的一个开源协作平台。 Mattermost 11.6.0及之前的11.6.x版本、11.5.3及之前的11.5.x版本、11.4.4及之前的11.4.x版本和10.11.14及之前的10.11.x版本存在安全漏洞，该漏洞源于处理出站Webhook附件有效载荷前未过滤nil元素，可能导致经过身份验证的用户通过包含空附件条目的特制Webhook回调响应造成拒绝服务。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of ServiceAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0≤ 11.6.0 |
affected |
11.5.0≤ 11.5.3 |
affected | ||
11.4.0≤ 11.4.4 |
affected | ||
10.11.0≤ 10.11.14 |
affected | ||
11.7.0 |
unaffected | ||
11.6.1 |
unaffected | ||
11.5.4 |
unaffected | ||
11.4.5 |
unaffected | ||
| … +1 more rows | |||
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I. Basic Information for CVE-2026-4915
Vulnerability Information
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Vulnerability Title
Server panic via outgoing webhook responses
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对因果或异常条件的不恰当检查
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.6.0及之前的11.6.x版本、11.5.3及之前的11.5.x版本、11.4.4及之前的11.4.x版本和10.11.14及之前的10.11.x版本存在安全漏洞，该漏洞源于处理出站Webhook附件有效载荷前未过滤nil元素，可能导致经过身份验证的用户通过包含空附件条目的特制Webhook回调响应造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 ~ 11.6.0 | - |
|
II. Public POCs for CVE-2026-4915
| # | POC Description | Source Link | Shenlong Link |
|---|
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IV. Related Vulnerabilities
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Same vendor: Mattermost
-
CVE-2026-75587
Plaintext pre-auth secret exposure via Desktop App diagnosti -
CVE-2026-9693
Mattermost thread memberships persist after team removal, ex -
CVE-2026-9859
Mattermost Boards plugin didn’t enforce role-based authoriza -
CVE-2026-9816
Insufficient server-side validation of board member role fie -
CVE-2026-10080
Boards plugin panics on WebSocket command with non-string fi
V. Comments for CVE-2026-4915
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