CVE-2026-55430
Coder allows organizations to provision remote development environments via Terraform.
Does this matter?
Lower severity and a low EPSS score (0.21%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 6.8 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N
- EPSS
- 0.21% probability · 11th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-345, CWE-441
- Affected
- coder/coder
- Source
- security-advisories@github.com
References
- https://github.com/coder/coder/pull/26204Issue Tracking, Patch
- https://github.com/coder/coder/releases/tag/v2.29.17Release Notes
- https://github.com/coder/coder/releases/tag/v2.32.7Release Notes
- https://github.com/coder/coder/releases/tag/v2.33.8Release Notes
- https://github.com/coder/coder/releases/tag/v2.34.2Release Notes
- https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478wPatch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.