CVE-2020-26232 in Server
Summary
by MITRE • 11/25/2020
Jupyter Server before version 1.0.6 has an Open redirect vulnerability. A maliciously crafted link to a jupyter server could redirect the browser to a different website. All jupyter servers are technically affected, however, these maliciously crafted links can only be reasonably made for known jupyter server hosts. A link to your jupyter server may appear safe, but ultimately redirect to a spoofed server on the public internet.
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Analysis
by VulDB Data Team • 12/10/2020
The vulnerability identified as CVE-2020-26232 represents a critical open redirect flaw within Jupyter Server versions prior to 1.0.6, creating a significant security risk for users and organizations relying on this popular data science platform. This vulnerability stems from inadequate input validation and sanitization mechanisms within the server's redirect handling functionality, allowing attackers to craft malicious URLs that could deceive users into navigating to unauthorized destinations. The flaw operates by exploiting the server's lack of proper validation when processing redirect parameters, enabling attackers to manipulate the redirect behavior through carefully constructed URI components.
The technical implementation of this vulnerability resides in the server's URL processing logic where user-supplied redirect parameters are not adequately validated against known safe destinations or hostnames. This creates a condition where an attacker can construct a malicious URL containing a redirect parameter pointing to an external domain, which the Jupyter Server will blindly follow without proper verification. The vulnerability is classified under CWE-601 as an Open Redirect vulnerability, which occurs when an application redirects users to external sites without proper validation, making it a direct descendant of the well-known web application security weakness. The flaw specifically affects the server's authentication and access control mechanisms, as users may be tricked into authenticating against a malicious server that mimics the legitimate Jupyter interface.
The operational impact of this vulnerability extends beyond simple phishing attacks, as it can enable sophisticated social engineering campaigns where attackers craft convincing URLs that appear to originate from trusted Jupyter servers. This opens the door for credential theft, session hijacking, and data exfiltration attacks where users unknowingly interact with malicious servers. The vulnerability is particularly dangerous in enterprise environments where Jupyter servers may be exposed to external networks, as attackers can exploit the knowledge of legitimate server hosts to create highly convincing malicious links. According to ATT&CK framework category T1566, this vulnerability enables initial access through social engineering techniques, while T1185 specifically addresses the use of credential harvesting through deceptive redirects, making this a multi-vector threat that can escalate into more serious security incidents.
Organizations should immediately implement mitigation strategies including updating to Jupyter Server version 1.0.6 or later, which contains the necessary patch to address the redirect validation issue. Additional defensive measures include implementing strict host validation policies within the server configuration, disabling unnecessary redirect functionality where possible, and deploying web application firewalls that can detect and block suspicious redirect patterns. Network-level controls such as DNS filtering and URL reputation services can provide additional layers of protection, while user education programs should emphasize the importance of verifying URLs before clicking on links, particularly those that appear to come from trusted internal systems. The vulnerability also highlights the importance of principle of least privilege in server configuration, where redirect functionality should be restricted to known safe destinations only, and all redirect operations should undergo strict validation against a whitelist of approved domains to prevent unauthorized redirection attempts.