Is CVE-2026-54338 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-54338?

CVE-2026-54338 has a CVSS v3 severity of MEDIUM (5.3).

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CVE-2026-54338

Description

JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0.