CVE-2026-55430
Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access
Description
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.
INFO
Published Date :
July 8, 2026, 1:16 a.m.
Last Modified :
July 8, 2026, 7:43 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Coder to version 2.34.2 or later.
- Configure an upstream reverse proxy.
- Strip or overwrite X-Forwarded-Host header.
- Ensure trusted proxies are configured.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55430.
| URL | Resource |
|---|---|
| https://github.com/coder/coder/pull/26204 | Issue Tracking Patch |
| https://github.com/coder/coder/releases/tag/v2.29.17 | Release Notes |
| https://github.com/coder/coder/releases/tag/v2.32.7 | Release Notes |
| https://github.com/coder/coder/releases/tag/v2.33.8 | Release Notes |
| https://github.com/coder/coder/releases/tag/v2.34.2 | Release Notes |
| https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w | Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55430 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55430
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55430 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55430 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N Added CPE Configuration OR *cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:* versions up to (excluding) 2.29.17 *cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:* versions from (including) 2.30.0 up to (excluding) 2.32.7 *cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:* versions from (including) 2.33.0 up to (excluding) 2.33.8 *cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:* versions from (including) 2.34.0 up to (excluding) 2.34.2 Added Reference Type GitHub, Inc.: https://github.com/coder/coder/pull/26204 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/coder/coder/releases/tag/v2.29.17 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/coder/coder/releases/tag/v2.32.7 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/coder/coder/releases/tag/v2.33.8 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/coder/coder/releases/tag/v2.34.2 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w Types: Patch, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 08, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-55430', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-08T16:57:10.249359Z'} -
New CVE Received by [email protected]
Jul. 08, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'coder', 'product': 'coder', 'versions': [{'status': 'affected', 'version': '>= 2.34.0, < 2.34.2'}, {'status': 'affected', 'version': '>= 2.33.0, < 2.33.8'}, {'status': 'affected', 'version': '>= 2.30.0, < 2.32.7'}, {'status': 'affected', 'version': '< 2.29.17'}]}] Added Description 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. Added CVSS V3.1 AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N Added CWE CWE-345 Added CWE CWE-441 Added Reference https://github.com/coder/coder/pull/26204 Added Reference https://github.com/coder/coder/releases/tag/v2.29.17 Added Reference https://github.com/coder/coder/releases/tag/v2.32.7 Added Reference https://github.com/coder/coder/releases/tag/v2.33.8 Added Reference https://github.com/coder/coder/releases/tag/v2.34.2 Added Reference https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w