CVE-2026-55455

Critical

Description

Appsmith is a platform to build admin panels, internal tools, and dashboards. Prior to 2.1, the outbound HTTP host filter applied by WebClientUtils (used by the REST API and GraphQL datasource plugins) validates hosts against an exact-match string denylist. The comprehensive address-class check (loopback, any-local, link-local, fc00::/7) exists only on a separate code path used by SMTP, not by the HTTP plugin path. As a result, an authenticated user can craft outbound requests that reach loopback-bound services inside the container. This vulnerability is fixed in 2.1.

SeverityCritical

CVSS9.1

Exploit probability—

ProductAppsmith

PublishedJun 24, 2026

First seenJun 24, 2026

Weakness typeCWE-918Server-side request forgery (SSRF)

How to fix

Update

appsmith appsmith2.1 or later

Affected products

Product	Affected versions	Fixed in
appsmith appsmith	v < 2.1	2.1

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