Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing

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Summary

CVECVE-2026-55438
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 01:16:28 UTC
Updated2026-07-08 01:16:28 UTC
DescriptionCoder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without confirming the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname. Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity. No known workarounds are available.

Risk And Classification

Primary CVSS: v3.1 5.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N

Problem Types: CWE-346 | CWE-346 CWE-346: Origin Validation Error

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
3.1CNADECLARED5.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Coder Coder affected >= 2.34.0, < 2.34.2 Not specified
CNA Coder Coder affected >= 2.33.0, < 2.33.8 Not specified
CNA Coder Coder affected >= 2.30.0, < 2.32.7 Not specified
CNA Coder Coder affected < 2.29.17 Not specified

References

ReferenceSourceLinkTags
github.com/coder/coder/releases/tag/v2.34.2 [email protected] github.com
github.com/coder/coder/security/advisories/GHSA-5wg6-jmq2-53pw [email protected] github.com
github.com/coder/coder/pull/26085 [email protected] github.com
github.com/coder/coder/releases/tag/v2.29.17 [email protected] github.com
github.com/coder/coder/releases/tag/v2.32.7 [email protected] github.com
github.com/coder/coder/pull/26086 [email protected] github.com
github.com/coder/coder/releases/tag/v2.33.8 [email protected] github.com
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