# What is CVE-2025-61669? > CVE-2025-61669 is a medium-severity flaw (CVSS 6.3) in Jupyter Server, published on 5 May 2026. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 0.2%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2025-61669 ## At a glance - **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle. - **Precursor Intelligence risk score:** 23 out of 100 (Low); action: Monitor. Kept up to date as the evidence changes. - **Severity:** Medium (CVSS 6.3 out of 10) - **Known to be exploited:** No, not on the list of flaws known to be exploited today - **Chance of use in the next 30 days:** 0.2% (latest exploit-likelihood forecast) - **Published:** 5 May 2026 - **Record last updated:** 7 October 2026 - **Main product:** Jupyter Server - **Affected products:** 1 ## What is CVE-2025-61669? In plain terms It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. ### The official description Jupyter Server is the backend for Jupyter web applications. In jupyter_server versions through 2.17.0, the next query parameter in the login flow is insufficiently validated in `LoginFormHandler._redirect_safe()`, which allows redirects to arbitrary external domains via values such as `///example.com`. An attacker can use a crafted login URL to redirect users to a malicious site and facilitate phishing attacks. This issue is fixed in version 2.18.0. ### What kind of flaw is it? - CWE-601: URL Redirection to Untrusted Site ('Open Redirect') ### How an attack on it works - Where an attacker can be: Anywhere on the internet - How hard it is to pull off: Easy: no special conditions - Login needed first: No login needed - Does someone have to click: Yes, a person has to take an action Severity vector: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X` ## Is CVE-2025-61669 being exploited? Not that we know of It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.2%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 0.2%, 0.2%, 0.2%, 0.2%, 0.2%, 0.2%, 0.2%. ### Timeline - 5 May 2026: Published - 7 October 2026: Record last updated ### How Precursor Intelligence ranks it CVE-2025-61669 scores **23 out of 100 (Low)**, with the action "Monitor". Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less: - Evidence it is being exploited: biggest factor - How severe it is: strong factor - How widely exposed it is: smaller factor - Threat activity around it: smaller factor 85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it. ## Who is affected by CVE-2025-61669? The published record lists 1 product. Versions are as published: "before 2.18.0" means every version up to, but not including, 2.18.0. - [Jupyter Server](https://www.precursorintelligence.com/product/jupyter/jupyter_server) by [Jupyter](https://www.precursorintelligence.com/vendors/jupyter) (Application): before 2.18.0 ## How do I fix CVE-2025-61669? 1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list. 2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list. 3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in. 4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood. ### References - [github.com](https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-qh7q-6qm3-653w) (Exploit, Vendor advisory) ## Questions ### What is CVE-2025-61669? CVE-2025-61669 is a medium-severity flaw in Jupyter Server, published on 5 May 2026. It can be attacked from anywhere on the internet without logging in, but a person has to take an action first. ### How serious is CVE-2025-61669? It scores 6.3 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2025-61669 is 23 out of 100, which is Low. Its action is "Monitor". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2025-61669 being exploited? It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.2%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2025-61669 affect? For Jupyter Server: before 2.18.0. ### How do I fix CVE-2025-61669? Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. ## Does CVE-2025-61669 affect you? Precursor Intelligence keeps checking for you: - **Tell us what you run.** Pick your software from a list, or let us work it out from your website. - **We match it to every flaw.** Over 400,000 published flaws, checked against your list. - **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it. - **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools. Start free (no card, nothing to install): https://www.precursorintelligence.com/register Book a demo: https://www.precursorintelligence.com/contact