Appsmith Appsmith — CVE-2026-55455 (Critical)

Date Jun 24, 2026

Type Vendor advisory

Signal Critical vendor advisory

Vendor / Product Appsmith · Appsmith

CVE CVE-2026-55455

Critical vendor advisory CVE-2026-55455

Summary

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.

Why it matters

This CVE carries a CRITICAL severity rating (CVSS 9.1) in Appsmith Appsmith. Patch or mitigate promptly. EPSS percentile: 13%.

Operator check

Review CVE-2026-55455 in your asset inventory. Apply patches per vendor guidance and verify Appsmith is not exposed. CVSS score: 9.1. EPSS probability: 0.2%; percentile: 13%.

Sources

NVD — CVE-2026-55455 Source reference

PatchBrief uses public sources. It does not scan environments, verify exposure, or replace vendor guidance.

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