CVE-2026-55438Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing
- 5.8MediumCVSS base score
- 0.22%Exploitation in 30 daysEPSS · top 87% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Coder 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.
Timeline
ID reserved
By GitHub_M
- 22 days later
· 22 days later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N |
| NVDNVD · Analyzed | 3.1 | Medium6.8 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.22% · top 87% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.8.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/coder/coder/v2GHSA-5wg6-jmq2-53pw (opens in a new tab)
References
References7
- https://github.com/coder/coder/security/advisories/GHSA-5wg6-jmq2-53pw (opens in a new tab)x_refsource_CONFIRM
- https://github.com/coder/coder/pull/26085 (opens in a new tab)x_refsource_MISC
- https://github.com/coder/coder/pull/26086 (opens in a new tab)x_refsource_MISC
- https://github.com/coder/coder/releases/tag/v2.29.17 (opens in a new tab)x_refsource_MISC
- https://github.com/coder/coder/releases/tag/v2.32.7 (opens in a new tab)x_refsource_MISC
- https://github.com/coder/coder/releases/tag/v2.33.8 (opens in a new tab)x_refsource_MISC
- https://github.com/coder/coder/releases/tag/v2.34.2 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-42151 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-5wg6-jmq2-53pw (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-55438)Record last updated .