PatchTheCVECVE-2026-58399: @acastellon/auth is an authentication control system for microservices
CVE-2026-58399 is a high-severity flaw (CVSS 8.7) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP
Why this priority
- High severity
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 8.7 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.0% (top 38%) |
| CISA exploited list | No |
| Weakness | CWE-287 |
| Published | 2026-07-01 |
| Last modified | 2026-10-25 |
Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-58399?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-58399 being exploited?
CVE-2026-58399 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-58399 affect?
CVE-2026-58399 affects affected software. Severity is high (CVSS 8.7). @acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateTo
How urgent is CVE-2026-58399?
Priority 51/100. High severity; Remotely exploitable, no login, no user action
Software pages
Brother printers vulnerabilities