CVE-2026-54338

mediumpriority · track · 0EPSS 0.004 · 38 %ileEUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.44% (38th) EPSS
CVSS 5.3 · medium
Is it mine?
3 products
Check your exposure
Who says so?
3 sources
cnnvd · enisa_euvd · osv

EPSS · scored 2026-10-28

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

5.3
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · ENISA EU
v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · security-advisories@github.comexploitability 3.9 · impact 1.4
v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · OSV
v3.14.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:Usecondary · CVSS-BT (t0sche)
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-400USCWE-400US
04

affected products (3)

Products and version ranges known to be affected.

  • jupyterhub jupyterhub≤ < 5.5.0JupyterHub 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.enisa_euvdEU
  • Bitnami jupyterhub< 5.5.0osvUSpkg:bitnami/jupyterhub
  • PyPI jupyterhub< 5.5.0osvUSpkg:pypi/jupyterhub
05

advisories (3)

Vendor and ecosystem advisories describing this.

  • GHSA-p43p-whwx-q52hJupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login2026-08-25ghsa · osvUS

    ### Impact Invalid input to login resulted in unbounded logging output. Only form-based Authenticators (the default PAM Authenticator, but not the more widely used OAuthenticator) are affected. ### Patches Upgrade to 5.5.0. ### Workarounds Use an Authenticator that doesn't use a login form, such as OAuthenticator.

  • BIT-jupyterhub-2026-54338JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login2026-09-29vendor · osvUS

    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.

  • PYSEC-2026-3853JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login2026-09-10vendor · osvUS

    ### Impact Invalid input to login resulted in unbounded logging output. Only form-based Authenticators (the default PAM Authenticator, but not the more widely used OAuthenticator) are affected. ### Patches Upgrade to 5.5.0. ### Workarounds Use an Authenticator that doesn't use a login form, such as OAuthenticator.

06

also known as (5)

Other names and identifiers for this entity.

07

sources

Which sources assert this record, and when.

cnnvdenisa_euvdosvNVDCVE.orgMITRE
published 2026-08-07modified 2026-08-11
08

references (6)

External citations — patches, advisories, analysis.

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