CVE-2020-15258: 
NixOS vulnerability analysis and mitigation

CVE-2020-15258 is a vulnerability in Wire Desktop's Electron application that was discovered in 2020. The vulnerability allows an attacker to execute arbitrary code on a victim's machine by sending messages containing links with arbitrary protocols. The issue was patched in version 3.20.x, while versions 3.19.x and earlier remain vulnerable (Wire Advisory).

The vulnerability exists due to the insecure implementation of Electron's shell.openExternal() function, which was used without proper URL validation. The application would pass all URLs directly to shell.openExternal(), allowing attackers to exploit various protocol handlers including SMB/CIFS on Windows, NFS on macOS, and custom protocol handlers. The issue was particularly exploitable on Linux systems where .desktop files could be executed through certain protocols (Shell Dangers).

When successfully exploited, this vulnerability allows attackers to execute arbitrary code on the victim's machine with the privileges of the current user. While the attack requires user interaction (such as middle-clicking a malicious link), the malicious URLs can be obfuscated to deceive users. The impact varies depending on the operating system, with different attack vectors available for Windows, macOS, and Linux systems (Wire Advisory).

The vulnerability can be triggered remotely by an attacker by sending a malicious message containing a specially crafted URL to a conversation. While exploitation requires user interaction (clicking the malicious link), the URL can be obfuscated to appear legitimate. The specific exploitation methods vary by operating system, with successful proof-of-concept exploits demonstrated particularly on Linux systems (Wire Advisory).

The vulnerability was patched in Wire Desktop version 3.20.x by implementing a helper function that checks URL protocols before opening them externally. The fix implements a strict allowlist that only permits common protocols (https:, http:, mailto:) and blocks potentially dangerous ones. When an unsafe URL is detected, the application displays a warning to the user instead of executing it (Wire Advisory).