Squid HTTPS Error Page Cross-Site Scripting Vulnerability [CVE-2018-19131]

CVE Number – CVE-2018-19131

A vulnerability in Squid could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack on a targeted system.The vulnerability is due to insufficient validation of user-supplied input by the affected software during the generation of HTTPS response messages related to Transport Layer Security (TLS) errors. An attacker could exploit this vulnerability by persuading a user to access an X.509 certificate that submits malicious input to the targeted system. A successful exploit could allow the attacker to conduct an XSS attack on the targeted system, which could lead to the execution of arbitrary script code in the context of the targeted user’s browser or allow the attacker to access sensitive browser-based information.Squid has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, the attacker may use misleading language or instructions to persuade a user to access an X.509 certificate that submits malicious input to the targeted system.

Safeguards

• Administrators are advised to apply the appropriate updates.
  
  Administrators are advised to allow only trusted users to have network access.
  
  Users are advised not to open email messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in email messages are safe, they are advised not to open them.
  
  Users are advised not to visit websites or follow links that have suspicious characteristics or cannot be verified as safe.
  
  Administrators are advised to use an unprivileged account when browsing the Internet.
  
  Administrators are advised to monitor critical systems.

Vendor Announcements

• Squid has released a security advisory at the following link: SQUID-2018:4

Fixed Software

• Squid has released software updates at the following link: Squid 4.4