Description
An issue was discovered in Squid through 4.7. When Squid is parsing ESI, it keeps the ESI elements in ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.
Remediation
References
Related Vulnerabilities
WordPress Plugin All In One Schema.org Rich Snippets Cross-Site Scripting (1.4.4)
MediaWiki Other Vulnerability (CVE-2004-2187)
WordPress Plugin Easy Testimonial Manager SQL Injection (1.2.0)
Jenkins Exposure of Sensitive Information to an Unauthorized Actor Vulnerability (CVE-2018-1999006)
Internet Information Services Other Vulnerability (CVE-1999-0154)