CVE-2026-55438: coder — Fix

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.

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CVSS v3.1 Score

5.8

MEDIUM

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

EPSS — Exploit Prediction

0.0022

Probability of exploitation

0.13%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-346 CWE-346

Affected Products

Vendor	Product	Versions
coder	coder	< 2.29.17
coder	coder	2.30.0 — 2.32.7
coder	coder	2.33.0 — 2.33.8
coder	coder	2.34.0 — 2.34.2

References

Advisories & Patches

https://github.com/coder/coder/pull/26085 https://github.com/coder/coder/pull/26086 https://github.com/coder/coder/security/advisories/GHSA-5wg6-jmq2-53pw

Other References

https://github.com/coder/coder/releases/tag/v2.29.17 https://github.com/coder/coder/releases/tag/v2.32.7 https://github.com/coder/coder/releases/tag/v2.33.8 https://github.com/coder/coder/releases/tag/v2.34.2

Frequently Asked Questions

What is CVE-2026-55438? +

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 has a CVSS v3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-55438? +

CVE-2026-55438 has a CVSS v3.1 score of 5.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0022, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-55438? +

CVE-2026-55438 affects products from coder, specifically: coder. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-55438? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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