Vulnerability in Coder

CVE-2026-55430

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (10.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 10th percentile — 10.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-55430: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

  • Coder — versions >= 2.34.0, < 2.34.2, >= 2.33.0, < 2.33.8, >= 2.30.0, < 2.32.7

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55430?
CVE-2026-55430 is a medium-severity vulnerability in Coder, classified under Insufficient Verification of Data Authenticity. CVSS score: 5.8/10. Published 2026-07-08.
How severe is CVE-2026-55430?
Medium severity. CVSS v3 base score is 5.8 out of 10.