Appsmith versions prior to server‑side request REST API and GraphQL datasource plugins. The HTTP outbound host filter relies on an exact‑match denylist and does not perform a comprehensive address‑class check for local or reserved IP ranges. Consequently, an authenticated user can craft requests that target loopback, any‑local, link‑local, or fc00::/7 addresses, allowing the application to communicate with services running inside the container. The weakness is identified as CWE‑918.

The vulnerability affects installations of Appsmith provided by appsmithorg. All releases before version 2.1 are susceptible; versions 2.1 and later include the fix.

The CVSS. The EPSS score is not available, so the exploitation probability is unknown at this time. The vulnerability is not listed in the CISA KEV catalog. An attacker who has authenticated access can exploit this flaw to reach internal services within the container, potentially exposing sensitive data or enabling further lateral movement. The attack vector requires valid credentials but can be carried out from any network that can reach the Appsmith instance.