Squid Digest Authentication Denial of Service Vulnerability [CVE-2019-12525]

CVE Number – CVE-2019-12525

A vulnerability in Squid could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability exists because the affected software does not sufficiently check proxy-authentication header length when Digest Authentication is enabled. An attacker could exploit this vulnerability by submitting a crafted HTTP request to the targeted system. A successful exploit could cause a DoS condition on the system. Squid has confirmed the vulnerability and released software updates.


  • To exploit this vulnerability, an attacker must send an HTTP request that submits malicious input to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.


  • Administrators are advised to apply the appropriate updates.

    Administrators are advised to allow only trusted users to have network access.

    Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.

    Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

    Administrators can help protect affected systems from external attacks by using a solid firewall strategy.

    Administrators are advised to monitor affected systems.

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Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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