CVE-2025-49590 in CryptPad
Summary
by MITRE • 06/19/2025
CryptPad is a collaboration suite. Prior to version 2025.3.0, the "Link Bouncer" functionality attempts to filter javascript URIs to prevent Cross-Site Scripting (XSS), however this can be bypassed. There is an "early allow" code path that happens before the URI's protocol/scheme is checked, which a maliciously crafted URI can follow. This issue has been patched in version 2025.3.0.
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Analysis
by VulDB Data Team • 08/12/2025
The vulnerability identified as CVE-2025-49590 affects CryptPad, a collaborative workspace platform that enables real-time document editing and file sharing. This security flaw resides within the application's Link Bouncer functionality, which is designed to prevent malicious hyperlinks from executing potentially harmful code. The primary concern emerges from the application's insufficient input validation mechanism that fails to properly sanitize user-provided URLs before processing them. The vulnerability represents a classic cross-site scripting weakness that could potentially allow attackers to inject malicious scripts into the application's interface.
The technical implementation of this vulnerability stems from a flawed code execution path within the URI validation logic. Specifically, the system contains an "early allow" mechanism that operates before the protocol scheme validation occurs. This premature allowance creates a window where maliciously crafted URIs can bypass the intended security checks. When a user inputs a specially crafted URL, the system initially permits the URI to proceed through an early validation step before performing the proper protocol verification. This architectural flaw allows JavaScript URIs to be processed without adequate sanitization, creating a direct pathway for XSS attacks. The vulnerability is classified as a CWE-79: Improper Neutralization of Input During Web Page Generation, which specifically addresses cross-site scripting issues in web applications. The issue also aligns with ATT&CK technique T1566.001: Phishing, as it enables the creation of malicious links that can be used in social engineering campaigns.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with potential access to user sessions and sensitive data within the collaborative environment. When exploited, the vulnerability could allow threat actors to inject malicious scripts that could steal session cookies, redirect users to phishing sites, or manipulate the application's functionality. The risk is particularly elevated in collaborative environments where users frequently share links and documents, as the attack surface expands with each shared resource. Attackers could craft malicious URIs that appear legitimate but contain embedded JavaScript payloads, potentially compromising multiple users within a shared workspace. The vulnerability's exploitation requires minimal technical knowledge, making it particularly dangerous in environments where users may not be security-aware.
The remediation for CVE-2025-49590 has been implemented in CryptPad version 2025.3.0, where the development team addressed the flawed early allow mechanism by reordering the validation logic to ensure protocol checking occurs before any URI processing. The fix implements proper input sanitization and validation that prevents JavaScript URIs from being processed through the vulnerable code path. Organizations should immediately update to the patched version to eliminate the risk of exploitation. Additionally, system administrators should monitor for any suspicious link sharing activities within the application and consider implementing additional network-level protections such as web application firewalls that can detect and block malicious URL patterns. The vulnerability demonstrates the importance of proper input validation and the potential consequences of inadequate security testing in collaborative software environments where user-generated content is prevalent.