Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
JupyterHub versions before 4.1.0 are affected. An attacker who tricks a user into visiting a malicious subdomain can use cookie tossing to trigger cross-site scripting that acts within the victim's session, potentially reaching the JupyterHub API and the user's single-user server. Upgrade to JupyterHub 4.1.0 or later, and enable domain-locked cookies by setting c.JupyterHub.cookie_host_prefix_enabled = True.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 8.1 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0033, the 26th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:36 UTC First seen by agentprime
- 31 Oct 2026, 14:36 UTC Confirmed by OSV