{"id":"CVE-2026-55430","state":"PUBLISHED","title":"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.","publishedAt":"2026-07-08T00:03:29.728Z","updatedAt":"2026-07-08T17:10:40.949Z","severity":{"score":5.8,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["coder coder"],"affected":[{"vendor":"coder","product":"coder","versions":[{"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","status":"affected"}]}],"references":["https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w","https://github.com/coder/coder/pull/26204","https://github.com/coder/coder/releases/tag/v2.29.17","https://github.com/coder/coder/releases/tag/v2.32.7","https://github.com/coder/coder/releases/tag/v2.33.8","https://github.com/coder/coder/releases/tag/v2.34.2"],"weaknesses":["CWE-345","CWE-441"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/55xxx/CVE-2026-55430.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55430","state":"PUBLISHED","datePublished":"2026-07-08T00:03:29.728Z","dateUpdated":"2026-07-08T17:10:40.949Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-16T21:59:57.017Z"},"containers":{"cna":{"title":"Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"coder","product":"coder","versions":[{"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","status":"affected"}]}],"references":[{"url":"https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w","name":"https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/coder/coder/pull/26204","name":"https://github.com/coder/coder/pull/26204","tags":["x_refsource_MISC"]},{"url":"https://github.com/coder/coder/releases/tag/v2.29.17","name":"https://github.com/coder/coder/releases/tag/v2.29.17","tags":["x_refsource_MISC"]},{"url":"https://github.com/coder/coder/releases/tag/v2.32.7","name":"https://github.com/coder/coder/releases/tag/v2.32.7","tags":["x_refsource_MISC"]},{"url":"https://github.com/coder/coder/releases/tag/v2.33.8","name":"https://github.com/coder/coder/releases/tag/v2.33.8","tags":["x_refsource_MISC"]},{"url":"https://github.com/coder/coder/releases/tag/v2.34.2","name":"https://github.com/coder/coder/releases/tag/v2.34.2","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.8,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"CHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-345","lang":"en","description":"CWE-345: Insufficient Verification of Data Authenticity","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-441","lang":"en","description":"CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-07-08T00:03:29.728Z"},"source":{"advisory":"GHSA-5g4w-3vw9-478w","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-08T16:57:10.249359Z","id":"CVE-2026-55430","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-08T17:10:40.949Z"}}]}}}