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CVE-2026-55455— Appsmith: SSRF in REST API / GraphQL datasource plugins via insufficient host denylist

Quick assessment

Affected
appsmithorg appsmith
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Appsmith是Appsmith团队开源的一个用于构建、部署和维护内部应用程序的开源平台。 Appsmith 2.1之前版本存在服务端请求伪造漏洞，该漏洞源于WebClientUtils应用的外发HTTP主机过滤器仅根据精确匹配字符串黑名单验证主机，而全面的地址类检查仅存在于SMTP的单独代码路径中，可能导致经过身份验证的用户构造外发请求访问容器内的回环绑定服务。

AI Predicted 9.8 Difficulty: Easy EPSS 0.39% · P32

Possible ATT&CK Techniques 1 AI

T1071.001 · Web Protocols

Affected Version Matrix 1

VendorProduct Version RangeStatus
appsmithorg appsmith < 2.1 affected
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I. Basic Information for CVE-2026-55455

Vulnerability Information
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Vulnerability Title
Appsmith: SSRF in REST API / GraphQL datasource plugins via insufficient host denylist
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Appsmith 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Appsmith是Appsmith团队开源的一个用于构建、部署和维护内部应用程序的开源平台。 Appsmith 2.1之前版本存在服务端请求伪造漏洞，该漏洞源于WebClientUtils应用的外发HTTP主机过滤器仅根据精确匹配字符串黑名单验证主机，而全面的地址类检查仅存在于SMTP的单独代码路径中，可能导致经过身份验证的用户构造外发请求访问容器内的回环绑定服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
appsmithorg appsmith < 2.1 -

II. Public POCs for CVE-2026-55455

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III. Intelligence Information for CVE-2026-55455

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Vendor Advisories for CVE-2026-55455 (1)

Same Patch Batch · appsmithorg · 2026-06-24 · 4 CVEs total

CVE-2026-55454 9.9 CRITICAL Appsmith: Caddy admin API exposed without authentication
CVE-2026-49979 Appsmith: SSRF via `POST /api/v1/admin/send-test-email` — JavaMail Bypasses WebClient IP F
CVE-2026-50189 Appsmith: RCE via Supervisord XML-RPC Admin Interface Exposed via /supervisor Caddy Route

IV. Related Vulnerabilities

Same product: appsmith
Same vendor: appsmithorg
Same weakness: CWE-918