CVE-2026-20719— DoS via URL Previews Rendering Malicious SVGs
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 11.4.0及之前的11.4.x版本、11.3.1及之前的11.3.x版本、11.2.3及之前的11.2.x版本和10.11.11及之前的10.11.x版本存在安全漏洞，该漏洞源于未能阻止链接嵌入中外部SVG的渲染，可能导致未经验证的用户通过创建GitHub问题或PR使Mattermost Web应用和桌面应用崩溃。
Possible ATT&CK Techniques 2 AI
T1552 · Unsecured Credentials T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-20719
Vulnerability Information
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Vulnerability Title
DoS via URL Previews Rendering Malicious SVGs
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to prevent rendering of external SVGs on link embeds which allows unauthenticated users to crash the Mattermost webapp and desktop app via creating an issue or PR on GitHub.. Mattermost Advisory ID: MMSA-2026-00595
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:L
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 11.4.0及之前的11.4.x版本、11.3.1及之前的11.3.x版本、11.2.3及之前的11.2.x版本和10.11.11及之前的10.11.x版本存在安全漏洞，该漏洞源于未能阻止链接嵌入中外部SVG的渲染，可能导致未经验证的用户通过创建GitHub问题或PR使Mattermost Web应用和桌面应用崩溃。
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 | 11.4.0 ~ 11.4.0 | - |
|
II. Public POCs for CVE-2026-20719
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-03-25 · 4 CVEs total
| CVE-2026-27656 | 5.7 MEDIUM | Account Takeover via Substring Matching in OpenID Connect Authentication |
| CVE-2026-27659 | 4.6 MEDIUM | CSRF vulnerability in UpdateAccessControlPolicyActiveStatus endpoint |
| CVE-2026-26233 | 4.3 MEDIUM | Denial of Service via HTTP/2 single packet attack on login endpoint |
IV. Related Vulnerabilities
Same product: Mattermost
-
CVE-2026-18799
Mattermost Server fails to restrict Slack import account bin -
CVE-2026-16251
Mattermost local image proxy allows server memory exhaustion -
CVE-2026-18256
Private team metadata disclosure via the team search API -
CVE-2026-18223
Mattermost invitation tokens not bound to invited email addr -
CVE-2026-19076
Mattermost fails to reject OAuth application sessions in acc
Same vendor: Mattermost
-
CVE-2026-18799
Mattermost Server fails to restrict Slack import account bin -
CVE-2026-16251
Mattermost local image proxy allows server memory exhaustion -
CVE-2026-18256
Private team metadata disclosure via the team search API -
CVE-2026-18223
Mattermost invitation tokens not bound to invited email addr -
CVE-2026-19076
Mattermost fails to reject OAuth application sessions in acc
Same weakness: CWE-754
V. Comments for CVE-2026-20719
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