CVE-2026-55455
Received Received - Intake
Outbound HTTP Loopback Access in Appsmith

Publication date: 2026-06-24

Last updated on: 2026-06-24

Assigner: GitHub, Inc.

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.
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Meta Information
Published
2026-06-24
Last Modified
2026-06-24
Generated
2026-06-25
AI Q&A
2026-06-25
EPSS Evaluated
N/A
NVD
CVE-2026-55455
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
appsmith appsmith 2.1
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
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Executive Summary

This vulnerability exists in Appsmith versions prior to 2.1, where the outbound HTTP host filter used by REST API and GraphQL datasource plugins only checks hosts against an exact-match denylist. Unlike the SMTP code path, it does not perform a comprehensive address-class check for loopback or local addresses. As a result, an authenticated user can craft outbound HTTP requests that reach loopback-bound services inside the container, potentially accessing internal services that should be protected.

Impact Analysis

The vulnerability allows an authenticated user to send outbound HTTP requests to loopback-bound services inside the container. This could lead to unauthorized access to internal services that are normally inaccessible from outside the container, potentially exposing sensitive internal data or functionality.

Mitigation Strategies

To mitigate this vulnerability, upgrade Appsmith to version 2.1 or later, where the issue with the outbound HTTP host filter has been fixed.

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