Coder up to 2.29.16/2.32.6/2.33.7/2.34.1 Workspace App Proxy RequestHost client-side enforcement of server-side security

Summaryinfo

A vulnerability described as critical has been identified in Coder up to 2.29.16/2.32.6/2.33.7/2.34.1. This affects the function RequestHost of the component Workspace App Proxy. The manipulation results in client-side enforcement of server-side security. This vulnerability is reported as CVE-2026-55430. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, was found in Coder up to 2.29.16/2.32.6/2.33.7/2.34.1. Affected is the function RequestHost of the component Workspace App Proxy. The manipulation with an unknown input leads to a client-side enforcement of server-side security vulnerability. CWE is classifying the issue as CWE-602. The product is composed of a server that relies on the client to implement a mechanism that is intended to protect the server. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the workspace app proxy resolves the target app from `httpapi.RequestHost()` which prefers the `X-Forwarded-Host` header over the real `Host` header. No middleware strips `X-Forwarded-Host` before routing and the header is not browser-forbidden so client-side JavaScript can set it on `fetch()` calls. Practical exploitation requires subdomain app routing (wildcard hostname) enabled, a victim who visits the attacker's shared app and a deployment whose upstream proxy does not strip `X-Forwarded-Host`. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 trusts `X-Forwarded-Host` only from configured trusted proxies and otherwise resolves the routing host from the verified request host. As a workaround, place an upstream reverse proxy that strips or overwrites `X-Forwarded-Host` on untrusted requests.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-55430 since 06/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 2.29.17, 2.32.7, 2.33.8 or 2.34.2 eliminates this vulnerability.

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Productinfo

Name

• Coder

Version

• 2.29.0
• 2.29.1
• 2.29.2
• 2.29.3
• 2.29.4
• 2.29.5
• 2.29.6
• 2.29.7
• 2.29.8
• 2.29.9
• 2.29.10
• 2.29.11
• 2.29.12
• 2.29.13
• 2.29.14
• 2.29.15
• 2.29.16
• 2.32.0
• 2.32.1
• 2.32.2
• 2.32.3
• 2.32.4
• 2.32.5
• 2.32.6
• 2.33.0
• 2.33.1
• 2.33.2
• 2.33.3
• 2.33.4
• 2.33.5
• 2.33.6
• 2.33.7
• 2.34.0
• 2.34.1

Website

• Product: https://github.com/coder/coder/

CPE 2.3info

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