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Vulnerability · Published Mar 25, 2026 · Assigned by Mattermost

CVE-2026-20719DoS via URL Previews Rendering Malicious SVGs

Medium 4.3

In plain English

A medium-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.4%top 70.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/mattermost/mattermost-server10.11.2+incompatible, 11.2.4+incompatible, 11.3.2+incompatible, 11.4.1+incompatibleGO-2026-5245
Gogithub.com/mattermost/mattermost-server/v5no fix listedGO-2026-5245
Gogithub.com/mattermost/mattermost-server/v6no fix listedGO-2026-5245
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260217110922-b7d4a1f1f59bGHSA-86vc-mg26-fj6x
Gogithub.com/mattermost/mattermost/server/v810.11.2GHSA-86vc-mg26-fj6x
Gogithub.com/mattermost/mattermost/server/v811.4.1GHSA-86vc-mg26-fj6x
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260217110922-b7d4a1f1f59bGO-2026-5245
Gogithub.com/mattermost/mattermost/server/v811.3.2GHSA-86vc-mg26-fj6x
Gogithub.com/mattermost/mattermost/server/v811.2.4GHSA-86vc-mg26-fj6x

Affected products (as reported)

VendorProductVersions
Mattermost Mattermost 11.4.0 – through 11.4.011.3.0 – through 11.3.111.2.0 – through 11.2.310.11.0 – through 10.11.11

Weakness: CWE-754 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

References