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CVE-2026-55438

Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing

No known exploitation. EPSS puts it in the 13th percentile. Fixed in 2.29.17.

CVSS 3.15.8MediumEPSS percentile13th0.2% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix2.29.17Upgrade to this build

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • CoderAffected: < 2.29.17Upgrade to: 2.29.17Stated by: NVD

Versions as the sources state them. Full version matrix after sign-in

What it is

From the CVE record

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.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS13th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.2% chance of exploitation activity in the next 30 days, which ranks it in the 13th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

4 events over 0 days, from the signal feeds we watch.

  1. Patch availablepublished, weakness classified, record updated

Affected products

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 5.8 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required LowRequires basic user-level privileges
  • User Interaction RequiredA user must click a link, open a file, or perform some action

Scope

  • Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity NoneNo integrity impact
  • Availability NoneNo availability impact

Weaknesses

Sources

References in the record

And 4 more references. See all after sign-in

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