Ubuntu Security Notice 6728-2 - USN-6728-1 fixed vulnerabilities in Squid. The fix for CVE-2023-5824 caused Squid to crash in certain environments on Ubuntu 20.04 LTS. The problematic fix has been reverted pending further investigation. Joshua Rogers discovered that Squid incorrectly handled collapsed forwarding. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service. This issue only affected Ubuntu 20.04 LTS and Ubuntu 22.04 LTS. Joshua Rogers discovered that Squid incorrectly handled certain structural elements. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service. Joshua Rogers discovered that Squid incorrectly handled Cache Manager error responses. A remote trusted client can possibly use this issue to cause Squid to crash, resulting in a denial of service. Joshua Rogers discovered that Squid incorrectly handled the HTTP Chunked decoder. A remote attacker could possibly use this issue to cause Squid to stop responding, resulting in a denial of service. Joshua Rogers discovered that Squid incorrectly handled HTTP header parsing. A remote trusted client can possibly use this issue to cause Squid to crash, resulting in a denial of service.