CVE-2026-55455: Appsmith: SSRF in REST API / GraphQL datasource plugins via insufficient host denylist
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Appsmithto a version that resolves this vulnerability.Fixed in 2.1
Event History
Frequently Asked Questions
What is the severity of CVE-2026-55455?
The severity of CVE-2026-55455 is medium with a CVSS score of 5.3.
How do I fix CVE-2026-55455?
To fix CVE-2026-55455, update Appsmith to version 2.1 or later, which addresses the insufficient host denylist issue.
What type of vulnerability is CVE-2026-55455?
CVE-2026-55455 is a Server-Side Request Forgery (SSRF) vulnerability.
What are the affected components in CVE-2026-55455?
The affected components in CVE-2026-55455 are the REST API and GraphQL datasource plugins in Appsmith.
When was CVE-2026-55455 published?
CVE-2026-55455 was published on June 24, 2026.