Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access
Summary
| CVE | CVE-2026-55430 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-08 01:16:27 UTC |
| Updated | 2026-07-08 19:43:14 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 6.8 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N
EPSS: 0.002080000 probability, percentile 0.109640000 (date 2026-07-10)
Problem Types: CWE-345 | CWE-441 | CWE-345 CWE-345: Insufficient Verification of Data Authenticity | CWE-441 CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 6.8 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N |
| 3.1 | [email protected] | Secondary | 5.8 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N |
| 3.1 | CNA | DECLARED | 5.8 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
RequiredScope
ChangedConfidentiality
HighIntegrity
NoneAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/coder/coder/releases/tag/v2.34.2 | [email protected] | github.com | Release Notes |
| github.com/coder/coder/pull/26204 | [email protected] | github.com | Issue Tracking, Patch |
| github.com/coder/coder/releases/tag/v2.29.17 | [email protected] | github.com | Release Notes |
| github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w | [email protected] | github.com | Patch, Vendor Advisory |
| github.com/coder/coder/releases/tag/v2.32.7 | [email protected] | github.com | Release Notes |
| github.com/coder/coder/releases/tag/v2.33.8 | [email protected] | github.com | Release Notes |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.