CVE-2020-25787 in Tiny RSS
Summary
by MITRE
An issue was discovered in Tiny Tiny RSS (aka tt-rss) before 2020-09-16. It does not validate all URLs before requesting them.
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Analysis
by VulDB Data Team • 12/23/2025
Tiny Tiny RSS represents a popular open source feed reader application that processes and displays RSS and Atom feeds from various sources. The vulnerability identified as CVE-2020-25787 stems from insufficient URL validation mechanisms within the application's feed processing pipeline. This weakness allows malicious actors to craft specially formatted feed entries containing harmful URLs that bypass the application's validation checks. The flaw specifically affects versions prior to the 2020-09-16 release, indicating a window of exposure where the application failed to properly sanitize or verify the legitimacy of URLs contained within feed data. This vulnerability operates at the application layer and can be classified under CWE-20, which encompasses improper input validation scenarios. The security implications extend beyond simple URL handling as the application's failure to validate URLs creates potential attack vectors for various malicious activities including but not limited to server-side request forgery attacks.
The technical execution of this vulnerability relies on the application's trust model where feed data is processed without adequate verification of URL formats, protocols, or destinations. When a user subscribes to a malicious feed or encounters compromised feed content, the application may attempt to fetch resources from URLs that appear legitimate but actually point to attacker-controlled resources. This behavior creates opportunities for attackers to leverage the application's feed fetching capabilities to access internal network resources, perform unauthorized data exfiltration, or redirect users to malicious websites. The vulnerability's impact is particularly concerning in environments where Tiny Tiny RSS serves as an organizational feed reader, as it could enable attackers to establish persistent access points or conduct reconnaissance activities against internal systems. From an attack perspective, this vulnerability aligns with ATT&CK technique T1071.004 which involves application layer protocol manipulation and can potentially enable further exploitation through techniques such as command and control communications.
The operational impact of CVE-2020-25787 extends beyond immediate security concerns to encompass potential data integrity and availability risks. Organizations utilizing vulnerable versions of Tiny Tiny RSS face the risk of unauthorized access to their internal infrastructure through feed processing mechanisms, particularly in scenarios where the application runs with elevated privileges or has network access to sensitive systems. The vulnerability's exploitation may not require sophisticated attack vectors, making it particularly dangerous as it can be leveraged through simple feed content manipulation. Network administrators should consider implementing monitoring for unusual outbound connections originating from feed processing services, as these could indicate exploitation attempts. The vulnerability's remediation requires updating to the patched version released on 2020-09-16, which likely incorporates enhanced URL validation routines and stricter input sanitization measures. Organizations should also implement feed validation policies and consider deploying network segmentation to limit the potential impact of compromised feed content. The vulnerability highlights the critical importance of validating all external inputs in web applications and demonstrates how seemingly minor validation gaps can create significant security exposure points.