Squid is an open source caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to Input Validation, Premature Release of Resource During Expected Lifetime, and Missing Release of Resource after Effective Lifetime bugs, Squid is vulnerable to Denial of Service attacks by a trusted server against all clients using the proxy. This bug is fixed in the default build configuration of Squid version 6.10.

Squid is a caching proxy for the Web. Due to an Uncontrolled Recursion bug in versions 2.6 through 2.7.STABLE9, versions 3.1 through 5.9, and versions 6.0.1 through 6.5, Squid may be vulnerable to a Denial of Service attack against HTTP Request parsing. This problem allows a remote client to perform Denial of Service attack by sending a large X-Forwarded-For header when the follow_x_forwarded_for feature is configured. This bug is fixed by Squid version 6.6. In addition, patches addressing this problem for the stable releases can be found in Squid's patch archives.

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to an Incorrect Check of Function Return Value bug Squid is vulnerable to a Denial of Service attack against its Helper process management. This bug is fixed by Squid version 6.5. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to a Buffer Overread bug Squid is vulnerable to a Denial of Service attack against Squid HTTP Message processing. This bug is fixed by Squid version 6.5. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to a NULL pointer dereference bug Squid is vulnerable to a Denial of Service attack against Squid's Gopher gateway. The gopher protocol is always available and enabled in Squid prior to Squid 6.0.1. Responses triggering this bug are possible to be received from any gopher server, even those without malicious intent. Gopher support has been removed in Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should reject all gopher URL requests.

A flaw was found in Squid. The limits applied for validation of HTTP response headers are applied before caching. However, Squid may grow a cached HTTP response header beyond the configured maximum size, causing a stall or crash of the worker process when a large header is retrieved from the disk cache, resulting in a denial of service.

SQUID is vulnerable to HTTP request smuggling, caused by chunked decoder lenience, allows a remote attacker to perform Request/Response smuggling past firewall and frontend security systems.

A buffer over-read was discovered in libntlmauth in Squid 2.5 through 5.6. Due to incorrect integer-overflow protection, the SSPI and SMB authentication helpers are vulnerable to reading unintended memory locations. In some configurations, cleartext credentials from these locations are sent to a client. This is fixed in 5.7.

In Squid 3.x through 3.5.28, 4.x through 4.17, and 5.x before 5.6, due to improper buffer management, a Denial of Service can occur when processing long Gopher server responses.

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. An integer overflow problem allows a remote server to achieve Denial of Service when delivering responses to HTTP Range requests. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent.

Squid before 4.15 and 5.x before 5.0.6 allows remote servers to cause a denial of service (affecting availability to all clients) via an HTTP response. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent by the server.

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to an input-validation bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy). A client sends an HTTP Range request to trigger this.

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a memory-management bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy) via HTTP Range request processing.

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to incorrect parser validation, it allows a Denial of Service attack against the Cache Manager API. This allows a trusted client to trigger memory leaks that. over time, lead to a Denial of Service via an unspecified short query string. This attack is limited to clients with Cache Manager API access privilege.

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a buffer-management bug, it allows a denial of service. When resolving a request with the urn: scheme, the parser leaks a small amount of memory. However, there is an unspecified attack methodology that can easily trigger a large amount of memory consumption.

An issue was discovered in Squid through 4.13 and 5.x through 5.0.4. Due to improper input validation, it allows a trusted client to perform HTTP Request Smuggling and access services otherwise forbidden by the security controls. This occurs for certain uri_whitespace configuration settings.

Squid through 4.14 and 5.x through 5.0.5, in some configurations, allows information disclosure because of an out-of-bounds read in WCCP protocol data. This can be leveraged as part of a chain for remote code execution as nobody.

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Smuggling attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the proxy cache and any downstream caches with content from an arbitrary source. When configured for relaxed header parsing (the default), Squid relays headers containing whitespace characters to upstream servers. When this occurs as a prefix to a Content-Length header, the frame length specified will be ignored by Squid (allowing for a conflicting length to be used from another Content-Length header) but relayed upstream.

Squid before 4.13 and 5.x before 5.0.4 allows a trusted peer to perform Denial of Service by consuming all available CPU cycles during handling of a crafted Cache Digest response message. This only occurs when cache_peer is used with the cache digests feature. The problem exists because peerDigestHandleReply() livelocking in peer_digest.cc mishandles EOF.