Squid is a caching proxy for the Web. In Squid versions prior to 7.2, a failure to redact HTTP authentication credentials in error handling allows information disclosure. The vulnerability allows a script to bypass browser security protections and learn the credentials a trusted client uses to authenticate. This potentially allows a remote client to identify security tokens or credentials used internally by a web application using Squid for backend load balancing. These attacks do not require Squid to be configured with HTTP authentication. The vulnerability is fixed in version 7.2. As a workaround, disable debug information in administrator mailto links generated by Squid by configuring squid.conf with emailerrdata off.

Squid 2.5, when processing the configuration file, parses empty Access Control Lists (ACLs), including proxyauth ACLs without defined auth schemes, in a way that effectively removes arguments, which could allow remote attackers to bypass intended ACLs if the administrator ignores the parser warnings.

Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero icpport). This problem cannot be mitigated by denying ICP queries using icpaccess rules. Version 7.5 contains a patch.

Squid has Denial of Service in ICP Response handling

Squid through 7.1 mishandles ASN.1 encoding of long SNMP OIDs. This occurs in asnbuildobjid in lib/snmplib/asn1.c.

Squid 2.5.STABLE9 and earlier does not trigger a fatal error when it identifies missing or invalid ACLs in the httpaccess configuration, which could lead to less restrictive ACLs than intended by the administrator.

Squid before 2.3STABLE5 in HTTP accelerator mode does not enable access control lists (ACLs) when the httpdaccelhost and httpaccelwithproxy off settings are used, which allows attackers to bypass the ACLs and conduct unauthorized activities such as port scanning.

squidldapauth in Squid 2.5 and earlier allows remote authenticated users to bypass username-based Access Control Lists (ACLs) via a username with a space at the beginning or end, which is ignored by the LDAP server.

Gibraltar Firewall 2.2 and earlier, when using the ClamAV update to 0.81 for Squid, uses a defunct ClamAV method to scan memory for viruses, which does not return an error code and prevents viruses from being detected.

Buffer overflows in Squid before 2.4.STABLE6 allow remote attackers to cause a denial of service (crash) and possibly execute arbitrary code (1) via the MSNT auth helper (msntauth) when using denyusers or allowusers files, (2) via the gopher client, or (3) via the FTP server directory listing parser when HTML output is generated.

FTP proxy in Squid before 2.4.STABLE6 does not compare the IP addresses of control and data connections with the FTP server, which allows remote attackers to bypass firewall rules or spoof FTP server responses.

Heap-based buffer overflow in Squid before 2.4 STABLE4, and Squid 2.5 and 2.6 until March 12, 2002 distributions, allows remote attackers to cause a denial of service, and possibly execute arbitrary code, via compressed DNS responses.

Squid 2.4 STABLE3 and earlier does not properly disable HTCP, even when "htcpport 0" is specified in squid.conf, which could allow remote attackers to bypass intended access restrictions.

Squid 2.4 STABLE3 and earlier allows remote attackers to cause a denial of service (core dump) and possibly execute arbitrary code with an ftp:// URL with a larger number of special characters, which exceed the buffer when Squid URL-escapes the characters.

The "%xx" URL decoding function in Squid 2.5STABLE4 and earlier allows remote attackers to bypass urlregex ACLs via a URL with a NULL ("%00") character, which causes Squid to use only a portion of the requested URL when comparing it against the access control lists.

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. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.

Squid is a caching proxy for the Web. In Squid versions prior to 7.2, a failure to redact HTTP authentication credentials in error handling allows information disclosure. The vulnerability allows a script to bypass browser security protections and learn the credentials a trusted client uses to authenticate. This potentially allows a remote client to identify security tokens or credentials used internally by a web application using Squid for backend load balancing. These attacks do not require Squid to be configured with HTTP authentication. The vulnerability is fixed in version 7.2. As a workaround, disable debug information in administrator mailto links generated by Squid by configuring squid.conf with emailerrdata off.

Squid is a caching proxy for the Web. Prior to version 7.5, due to premature release of resource during expected lifetime and heap Use-After-Free bugs, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero icpport). This problem cannot be mitigated by denying ICP queries using icpaccess rules. This bug is fixed in Squid version 7.5.

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero icpport). This problem cannot be mitigated by denying ICP queries using icpaccess rules. Version 7.5 contains a patch.

Squid has issues in ICP message handling

Squid is a caching proxy for the Web. Prior to 7.6, due to an improper validation of syntactic correctness of input in the FTP gateway (src/clients/FtpGateway.cc), Squid is vulnerable to an out-of-bounds read: when a listing entry date in the TypeA or TypeB directory-listing formats is not followed by a filename, parsing was not restricted to the input buffer, so a trusted client accessing a misbehaving FTP server through Squid's gateway feature could read memory from random unrelated transactions. This issue is fixed in version 7.6.

Squid 2.5 STABLE9 and earlier, when the DNS client port is unfiltered and the environment does not prevent IP spoofing, allows remote attackers to spoof DNS lookups.

Squid is a caching proxy for the Web. Prior to 7.6, due to an improper input validation bug in cache digest reply handling (peerDigestSwapInMask in src/peerdigest.cc), Squid is vulnerable to a heap-based buffer overflow: a cache digest's on-the-wire size may be larger than the masksize declared within the digest, so a trusted peer sending a maliciously crafted reply to a cachedigest request message can trigger the overflow. This attack is limited to Squid instances compiled with the --enable-cache-digests option and configured with cachepeer entries. This issue is fixed in version 7.6.

Common Vulnerabilities and Exposures assigned an identifier CVE-2009-0801 to the following vulnerability:

Name: CVE-2009-0801 URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0801 Assigned: 20090304 Reference: CERT-VN:VU#435052 Reference: URL: http://www.kb.cert.org/vuls/id/435052 Reference: BID:33858 Reference: URL: http://www.securityfocus.com/bid/33858

Squid, when transparent interception mode is enabled, uses the HTTP Host header to determine the remote endpoint, which allows remote attackers to bypass access controls for Flash, Java, Silverlight, and probably other technologies, and possibly communicate with restricted intranet sites, via a crafted web page that causes a client to send HTTP requests with a modified Host header.

Squid proxy server 2.4 and earlier allows remote attackers to cause a denial of service (crash) via a mkdir-only FTP PUT request.

Squid 2.5.STABLE10 and earlier, while performing NTLM authentication, does not properly handle certain request sequences, which allows attackers to cause a denial of service (daemon restart).

Squid 2.5.STABLE7 and earlier allows remote attackers to cause a denial of service (segmentation fault) by aborting the connection during a (1) PUT or (2) POST request, which causes Squid to access previously freed memory.

Squid 2.5 up to 2.5.STABLE7 allows remote attackers to poison the cache or conduct certain attacks via headers that do not follow the HTTP specification, including (1) multiple Content-Length headers, (2) carriage return (CR) characters that are not part of a CRLF pair, and (3) header names containing whitespace characters.