SSRF in GitHub Enterprise Server Notebook Viewer (3.20.2)
CVE-2026-8034 Published on May 7, 2026
Server-side request forgery vulnerability in GitHub Enterprise Server notebook viewer via URL parser confusion
A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.
Vulnerability Analysis
CVE-2026-8034 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Types
What is a SSRF Vulnerability?
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
CVE-2026-8034 has been classified to as a SSRF vulnerability or weakness.
Interpretation Conflict
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state. This is generally found in proxies, firewalls, anti-virus software, and other intermediary devices that monitor, allow, deny, or modify traffic based on how the client or server is expected to behave.
Products Associated with CVE-2026-8034
Want to know whenever a new CVE is published for github Enterprise Server? stack.watch will email you.
Affected Versions
GitHub Enterprise Server:- Version 3.16.0, <= 3.16.17 is affected.
- Version 3.17.0, <= 3.17.14 is affected.
- Version 3.18.0, <= 3.18.8 is affected.
- Version 3.19.0, <= 3.19.5 is affected.
- Version 3.20.0, <= 3.20.1 is affected.
- Version 3.21.0 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.