CVE’s

An issue was discovered in Squid 4.0.23 through 4.7. When checking Basic Authentication with HttpHeader::getAuth, Squid uses a global buffer to store the decoded data. Squid does not check that the decoded length isn't greater than the buffer, leading to a heap-based buffer overflow with user controlled data.

An issue was discovered in Squid before 4.9. URN response handling in Squid suffers from a heap-based buffer overflow. When receiving data from a remote server in response to an URN request, Squid fails to ensure that the response can fit within the buffer. This leads to attacker controlled data overflowing in the heap.

An issue was discovered in Squid 3.3.9 through 3.5.28 and 4.x through 4.7. When Squid is configured to use Digest authentication, it parses the header Proxy-Authorization. It searches for certain tokens such as domain, uri, and qop. Squid checks if this token's value starts with a quote and ends with one. If so, it performs a memcpy of its length minus 2. Squid never checks whether the value is just a single quote (which would satisfy its requirements), leading to a memcpy of its length minus 1.

An issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to see if the request should be denied. Squid by default comes with rules to block access to the Cache Manager, which serves detailed server information meant for the maintainer. This rule is implemented via url_regex. The handler for url_regex rules URL decodes an incoming request. This allows an attacker to encode their URL to bypass the url_regex check, and gain access to the blocked resource.

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.

An issue was discovered in Squid through 4.7. When Squid is run as root, it spawns its child processes as a lesser user, by default the user nobody. This is done via the leave_suid call. leave_suid leaves the Saved UID as 0. This makes it trivial for an attacker who has compromised the child process to escalate their privileges back to root.

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.

An issue was discovered in Squid through 4.7 and 5. When receiving a request, Squid checks its cache to see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request. If found, it servers the request. The absolute URL can include the decoded UserInfo (username and password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to provide a username that has special characters to delimit the domain, and treat the rest of the URL as a path or query string. An attacker could first make a request to their domain using an encoded username, then when a request for the target domain comes in that decodes to the exact URL, it will serve the attacker's HTML instead of the real HTML. On Squid servers that also act as reverse proxies, this allows an attacker to gain access to features that only reverse proxies can use, such as ESI.

An information disclosure vulnerability exists when the Windows GDI component improperly discloses the contents of its memory, aka 'Windows GDI Information Disclosure Vulnerability'. This CVE ID is unique from CVE-2019-1286.

An issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate. This function uses a fixed stack buffer to hold the expression while it's being evaluated. When processing the expression, it could either evaluate the top of the stack, or add a new member to the stack. When adding a new member, there is no check to ensure that the stack won't overflow.