An issue was discovered in Squid before 4.9. When handling a URN request, a corresponding HTTP request is made. This HTTP request doesn't go through the access checks that incoming HTTP requests go through. This causes all access checks to be bypassed and allows access to restricted HTTP servers, e.g., an attacker can connect to HTTP servers that only listen on localhost.

Affected: Ubuntu:16.04:LTS: squid3, Ubuntu:18.04:LTS: squid3

Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly handled certain URN requests. A remote attacker could possibly use this issue to bypass access checks and access restricted servers. This issue was only addressed in Ubuntu 19.04 and Ubuntu 19.10. (CVE-2019-12523)

Jeriko One discovered that Squid incorrectly handed URN responses. A remote attacker could use this issue to cause Squid to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2019-12526)

Alex Rousskov discovered that Squid incorrectly handled certain strings. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service. This issue only affected Ubuntu 19.04. (CVE-2019-12854)

Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly handled certain input. A remote attacker could use this issue to cause Squid to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue was only addressed in Ubuntu 19.04 and Ubuntu 19.10. (CVE-2019-18676)

Kristoffer Danielsson discovered that Squid incorrectly handled certain messages. This issue could result in traffic being redirected to origins it should not be delivered to. (CVE-2019-18677)

Régis Leroy discovered that Squid incorrectly handled certain HTTP request headers. A remote attacker could use this to smuggle HTTP requests and corrupt caches with arbitrary content. (CVE-2019-18678)

David Fifield discovered that Squid incorrectly ha…