CVE-2021-41178 is a vulnerability in Nextcloud Server
Published on October 25, 2021
File Traversal affecting SVG files on Nextcloud Server
Nextcloud is an open-source, self-hosted productivity platform. Prior to versions 20.0.13, 21.0.5, and 22.2.0, a file traversal vulnerability makes an attacker able to download arbitrary SVG images from the host system, including user provided files. This could also be leveraged into a XSS/phishing attack, an attacker could upload a malicious SVG file that mimics the Nextcloud login form and send a specially crafted link to victims. The XSS risk here is mitigated due to the fact that Nextcloud employs a strict Content-Security-Policy disallowing execution of arbitrary JavaScript. It is recommended that the Nextcloud Server be upgraded to 20.0.13, 21.0.5 or 22.2.0. There are no known workarounds aside from upgrading.
Vulnerability Analysis
CVE-2021-41178 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Types
Relative Path Traversal
The software uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory. This allows attackers to traverse the file system to access files or directories that are outside of the restricted directory.
What is an Unrestricted File Upload Vulnerability?
The software allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment.
CVE-2021-41178 has been classified to as an Unrestricted File Upload vulnerability or weakness.
Products Associated with CVE-2021-41178
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Affected Versions
nextcloud security-advisories:- Version 20.0.13 is affected.
- Version >= 21.0.0, < 21.0.5 is affected.
- Version < 22.2.0 is affected.
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.