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TI-2026-39998 Aliases CVE-2026-55430GHSA-5g4w-3vw9-478w

Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access

Priority LOW 29CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
Required
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-345.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00208 11th percentileScored 2026-11-07
Fix Fixed coder (coder): 2.34.2, 2.33.8, 2.32.7 +1github.com/coder/coder/v2 (Go): 2.34.2, 2.33.8, 2.32.7 +1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
codercoder2.34.0 to before 2.34.2; 2.33.0 to before 2.33.8; 2.30.0 to before 2.32.7; before 2.29.172.34.2, 2.33.8, 2.32.7, 2.29.17Patch availableCNA
—github.com/coder/coder/v2 (Go)2.34.0 to before 2.34.22.34.2Patch availableGHSA-5g4w-3vw9-478w
—github.com/coder/coder/v2 (Go)2.33.0 to before 2.33.82.33.8Patch availableGHSA-5g4w-3vw9-478w
—github.com/coder/coder/v2 (Go)2.30.0 to before 2.32.72.32.7Patch availableGHSA-5g4w-3vw9-478w
—github.com/coder/coder/v2 (Go)before 2.29.172.29.17Patch availableGHSA-5g4w-3vw9-478w
  • coder Vendorcoder Affected 2.34.0 to before 2.34.2; 2.33.0 to before 2.33.8; 2.30.0 to before 2.32.7; before 2.29.17 Fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17 Patch available CNA
  • github.com/coder/coder/v2 (Go) Vendor— Affected 2.34.0 to before 2.34.2 Fixed in 2.34.2 Patch available GHSA-5g4w-3vw9-478w
  • github.com/coder/coder/v2 (Go) Vendor— Affected 2.33.0 to before 2.33.8 Fixed in 2.33.8 Patch available GHSA-5g4w-3vw9-478w
  • github.com/coder/coder/v2 (Go) Vendor— Affected 2.30.0 to before 2.32.7 Fixed in 2.32.7 Patch available GHSA-5g4w-3vw9-478w
  • github.com/coder/coder/v2 (Go) Vendor— Affected before 2.29.17 Fixed in 2.29.17 Patch available GHSA-5g4w-3vw9-478w

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:*before 2.29.17; 2.30.0 to before 2.32.7; 2.33.0 to before 2.33.8; 2.34.0 to before 2.34.2Vulnerablecoder
  • cpe:2.3:a:coder:coder:*:*:*:*:*:go:*:* Versions before 2.29.17; 2.30.0 to before 2.32.7; 2.33.0 to before 2.33.8; 2.34.0 to before 2.34.2 Vulnerable ·coder

Remediation

  • Fix · CNA coder (coder) Fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17
  • Fix · GHSA-5g4w-3vw9-478w github.com/coder/coder/v2 (Go) Fixed in 2.34.2 Advisory →
  • Fix · GHSA-5g4w-3vw9-478w github.com/coder/coder/v2 (Go) Fixed in 2.33.8 Advisory →
  • Fix · GHSA-5g4w-3vw9-478w github.com/coder/coder/v2 (Go) Fixed in 2.32.7 Advisory →
  • Fix · GHSA-5g4w-3vw9-478w github.com/coder/coder/v2 (Go) Fixed in 2.29.17 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55430
  2. 2026-10-03 Alias added: GHSA-5g4w-3vw9-478w

References

Patch 2

Other 5

  • TI-2026-34071 Coder: PKCS#7 signature bypass in Azure instance identity allows unauthenticated agent token theft CVSS 3.1CRITICAL 9.1
  • TI-2026-32394 Coder vulnerable to workspace auto-creation via crafted URL parameters without user consent CVSS 3.1HIGH 8.8
  • TI-2024-18523 Coder's OIDC authentication allows email with partially matching domain to register CVSS 3.1HIGH 8.2
  • TI-2026-39997 Coder's workspace app upsert allows cross-workspace agent rebinding via user-controlled app ID CVSS 3.1HIGH 8.7
  • TI-2026-39996 Coder: Route hijacking through lack of validation of agent-supplied AllowedIPs in tailnet coordinator CVSS 3.1HIGH 8.2
  • TI-2026-39995 Coder vulnerable to SSH config injection via unsanitized server-supplied values in `coder config-ssh` CVSS 3.1HIGH 8.3
See all 22 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences