How severe is CVE-2020-26261?

CVE-2020-26261 has a CVSS 3.x base score of 7.9, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2020-26261 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-26261?

CVE-2020-26261 affects Jupyterhub Systemdspawner. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-26261?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-26261 published?

CVE-2020-26261 was published on 2020-12-09 and last updated on 2026-06-17.

CVE-2020-26261

CVE-2020-26261 is a high-severity vulnerability in Jupyterhub Systemdspawner with a CVSS 3.x base score of 7.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-668.

Key facts

Severity: High (CVSS 3.x base score 7.9)
CVSS v2: 3.3
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-668
Affected product: Jupyterhub Systemdspawner
Published: 2020-12-09
Last modified: 2026-06-17

Description

jupyterhub-systemdspawner enables JupyterHub to spawn single-user notebook servers using systemd. In jupyterhub-systemdspawner before version 0.15 user API tokens issued to single-user servers are specified in the environment of systemd units. These tokens are incorrectly accessible to all users. In particular, the-littlest-jupyterhub is affected, which uses systemdspawner by default. This is patched in jupyterhub-systemdspawner v0.15

Frequently asked questions

What is CVE-2020-26261?: jupyterhub-systemdspawner enables JupyterHub to spawn single-user notebook servers using systemd. In jupyterhub-systemdspawner before version 0.15 user API tokens issued to single-user servers are specified in the environment of systemd units. These tokens are incorrectly accessible to all users. In particular, the-littlest-jupyterhub is affected, which uses systemdspawner by default. This is patched in jupyterhub-systemdspawner v0.15
How severe is CVE-2020-26261?: CVE-2020-26261 has a CVSS 3.x base score of 7.9, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2020-26261 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-26261?: CVE-2020-26261 affects Jupyterhub Systemdspawner. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-26261?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-26261 published?: CVE-2020-26261 was published on 2020-12-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:jupyterhub:systemdspawner:*:*:*:*:*:*:*:*

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