CVE-2020-26215: 
Python vulnerability analysis and mitigation

Jupyter Notebook before version 6.1.5 contains an Open Redirect vulnerability (CVE-2020-26215). The vulnerability was discovered by zhuonan li of Alibaba Application Security Team and disclosed on November 18, 2020. This security issue affects Jupyter Notebook servers, allowing maliciously crafted links to redirect users to different websites (GitHub Advisory).

The vulnerability exists in the URL handling mechanism of Jupyter Notebook servers. The issue stems from insufficient validation of URLs, where a maliciously crafted link to a notebook server could redirect the browser to a different website. This vulnerability is particularly concerning for known notebook server hosts, where links may appear safe but ultimately redirect to spoofed servers on the public internet (GitHub Advisory).

The vulnerability allows attackers to create malicious links that appear to point to legitimate Jupyter Notebook servers but redirect users to potentially malicious websites. While all notebook servers are technically affected, the exploitation risk is higher for known notebook server hosts. This could lead to phishing attacks or other malicious redirections (GitHub Advisory).

The vulnerability can be exploited by crafting specific URLs that target known Jupyter Notebook server hosts. An attacker needs to create a malicious link that appears legitimate but contains specially crafted parameters to trigger the redirect. The vulnerability is particularly effective when targeting known notebook server installations (GitHub Advisory).

The vulnerability has been patched in Jupyter Notebook version 6.1.5. Users are strongly recommended to upgrade to this version or later. Various distributions have also released security updates, including Ubuntu 18.04 LTS and 20.04 LTS, and Debian 9 'Stretch' (version 4.2.3-4+deb9u2) (Ubuntu Notice, Debian LTS).