CVE-2026-55438 (GCVE-0-2026-55438)

Vulnerability from cvelistv5 – Published: 2026-07-08 00:31 – Updated: 2026-07-08 17:10
VLAI
Title
Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing
Summary
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.
Severity
5.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-346 - Origin Validation Error
Assigner
References
Impacted products
Vendor Product Version
coder coder Affected: >= 2.34.0, < 2.34.2
Affected: >= 2.33.0, < 2.33.8
Affected: >= 2.30.0, < 2.32.7
Affected: < 2.29.17
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.