CVE-2019-12521 Explained : Impact and Mitigation

A vulnerability has been found in Squid version 4.7 and earlier versions, leading to a Heap Overflow during ESI parsing.

Understanding CVE-2019-12521

This CVE involves a specific vulnerability in Squid versions 4.7 and below related to ESI parsing.

What is CVE-2019-12521?

This vulnerability in Squid occurs during the parsing of ESI (Edge Side Includes) elements, specifically within the ESIContext buffer structure.

The Impact of CVE-2019-12521

The vulnerability results in a Heap Overflow of 1 element within the ESIContext buffer, causing Squid to crash during processing.

Technical Details of CVE-2019-12521

This section provides more in-depth technical insights into the CVE.

Vulnerability Description

Squid incorrectly checks the number of elements in the ESIContext buffer, leading to a Heap Overflow of 1 element.

Affected Systems and Versions

Squid version 4.7 and earlier versions are affected by this vulnerability.

Exploitation Mechanism

During ESI parsing, the addStackElement function's incorrect check for the buffer's elements triggers the Heap Overflow.

Mitigation and Prevention

Protect your systems from CVE-2019-12521 with these mitigation strategies.

Immediate Steps to Take

Update Squid to a non-vulnerable version.
Monitor vendor advisories for patches and apply them promptly.

Long-Term Security Practices

Regularly update and patch software to prevent vulnerabilities.

Patching and Updates

Stay informed about security updates and apply them as soon as they are available.