CVE-2026-55438Network attack vector

Credentialed cross-origin data theft via UUID subdomain spoofing

Published Jul 8, 2026 · Updated Jul 8, 2026

Origin validation error in affected Coder releases allows remote authenticated users to read workspace app data through crafted subdomains. When a workspace-name segment parses as a UUID, the proxy resolves the workspace by ID without matching the hostname username to its owner, and CORS trusts that unverified username. Subdomain app routing must be enabled, and an authenticated victim must visit the attacker's URL before credentialed JavaScript reads responses from the victim's workspace apps.

CVSS severity5.8
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Origin validation error in affected Coder releases allows remote authenticated users to read workspace app data through crafted subdomains. When a workspace-name segment parses as a UUID, the proxy resolves the workspace by ID without matching the hostname username to its owner, and CORS trusts that unverified username. Subdomain app routing must be enabled, and an authenticated victim must visit the attacker's URL before credentialed JavaScript reads responses from the victim's workspace apps.

The record

CVE
CVE-2026-55438
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Coder
Product
Coder
Classifications
CWE-346
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.29.17
  2. Affected versionversion=>= 2.30.0, < 2.32.7
  3. Affected versionversion=>= 2.33.0, < 2.33.8
  4. Affected versionversion=>= 2.34.0, < 2.34.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Coder · Coderversion=< 2.29.17; version=>= 2.30.0, < 2.32.7; version=>= 2.33.0, < 2.33.8; version=>= 2.34.0, < 2.34.2

Published CVSS scores

5.8GitHubCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
6.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-346Origin Validation Error

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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