coder Workspace App Proxy up to 2.29.16/2.32.6/2.33.7/2.34.1 cross-domain policy

Summaryinfo

A vulnerability identified as problematic has been detected in coder Workspace App Proxy up to 2.29.16/2.32.6/2.33.7/2.34.1. This affects an unknown part. The manipulation leads to cross-domain policy. This vulnerability is listed as CVE-2026-55438. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in coder Workspace App Proxy up to 2.29.16/2.32.6/2.33.7/2.34.1 and classified as problematic. This issue affects some unknown functionality. The manipulation with an unknown input leads to a cross-domain policy vulnerability. Using CWE to declare the problem leads to CWE-942. The product uses a cross-domain policy file that includes domains that should not be trusted. Impacted is confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-55438 since 06/16/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 2.29.17, 2.32.7, 2.33.8 or 2.34.2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-42151). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Firewall Software

Vendor

• coder

Name

• Workspace App Proxy

Version

• 2.29.0
• 2.29.1
• 2.29.2
• 2.29.3
• 2.29.4
• 2.29.5
• 2.29.6
• 2.29.7
• 2.29.8
• 2.29.9
• 2.29.10
• 2.29.11
• 2.29.12
• 2.29.13
• 2.29.14
• 2.29.15
• 2.29.16
• 2.32.0
• 2.32.1
• 2.32.2
• 2.32.3
• 2.32.4
• 2.32.5
• 2.32.6
• 2.33.0
• 2.33.1
• 2.33.2
• 2.33.3
• 2.33.4
• 2.33.5
• 2.33.6
• 2.33.7
• 2.34.0
• 2.34.1

CPE 2.3info

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• 🔒
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CPE 2.2info

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• 🔒
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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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