{"id":"GHSA-5wg6-jmq2-53pw","summary":"Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing","details":"### Summary\n\nCoder'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.\n\n\u003e **Note:** Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated.\n\n### Impact\n\nAn authenticated user could craft a subdomain encoding their own workspace UUID and a victim's username. If the victim visited the attacker's URL, the attacker's JavaScript could issue credentialed cross-origin `fetch()` requests to the victim's workspace apps and read the responses, exfiltrating data accessible through those apps.\n\n### Patches\n\nThe fix validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity.\n\nThe fix was backported to all supported release lines:\n\n| Release line | Patched version |\n|---|---|\n| 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) |\n| 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) |\n| 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) |\n| 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) |\n\n### Workarounds\n\nNone.\n\n### Resources\n\n- Fix: #26086, #26085\n\n### Credits\n\nCoder would like to thank Anthropic's Security Team (ANT-2026-22434) for independently disclosing this issue!","aliases":["CVE-2026-55438","GO-2026-5918"],"modified":"2026-07-07T20:41:23.472240752Z","published":"2026-07-06T21:14:49Z","database_specific":{"github_reviewed_at":"2026-07-06T21:14:49Z","nvd_published_at":null,"cwe_ids":["CWE-346"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/coder/coder/security/advisories/GHSA-5wg6-jmq2-53pw"},{"type":"WEB","url":"https://github.com/coder/coder/pull/26085"},{"type":"WEB","url":"https://github.com/coder/coder/pull/26086"},{"type":"PACKAGE","url":"https://github.com/coder/coder"}],"affected":[{"package":{"name":"github.com/coder/coder/v2","ecosystem":"Go","purl":"pkg:golang/github.com/coder/coder/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.34.0"},{"fixed":"2.34.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-5wg6-jmq2-53pw/GHSA-5wg6-jmq2-53pw.json"}},{"package":{"name":"github.com/coder/coder/v2","ecosystem":"Go","purl":"pkg:golang/github.com/coder/coder/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.33.0"},{"fixed":"2.33.8"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-5wg6-jmq2-53pw/GHSA-5wg6-jmq2-53pw.json"}},{"package":{"name":"github.com/coder/coder/v2","ecosystem":"Go","purl":"pkg:golang/github.com/coder/coder/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.30.0"},{"fixed":"2.32.7"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-5wg6-jmq2-53pw/GHSA-5wg6-jmq2-53pw.json"}},{"package":{"name":"github.com/coder/coder/v2","ecosystem":"Go","purl":"pkg:golang/github.com/coder/coder/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.29.17"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-5wg6-jmq2-53pw/GHSA-5wg6-jmq2-53pw.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N"}]}