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 email_err_data off.
Due to an error in the exception handling mechanism (CWE-209, CWE-550), Squid exposes HTTP authentication credentials in error messages that should be redacted before display. A malicious script can read this data from the error response content, bypassing standard browser security measures. The attack does not require Squid to be configured with HTTP authentication support — it is sufficient that the proxy processes traffic from web applications using Squid for backend load balancing.
A remote attacker can obtain security tokens or authentication credentials used internally by web applications, potentially hijacking sessions or gaining unauthorized access to protected resources.
Squid should be updated to version 7.2, where the vulnerability has been fixed. As a temporary workaround, debug information inclusion in mailto administrator links can be disabled by adding the following directive to the squid.conf file: email_err_data off.
Squid-Cache Squid in all versions prior to 7.2
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:NSquid Cache Squid
APPSquid-Cache< 7.2
Related vulnerabilities
Squid: Use-After-Free w obsłudze ruchu ICP umożliwia atak DoS
Heap buffer overflow w Squid podczas przetwarzania URN – możliwy RCE
SQUID is vulnerable to HTTP request smuggling, caused by chunked decoder lenience, allows a remote attacker to...
An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A Reque...
An issue was discovered in Squid before 5.0.2. A remote attacker can replay a sniffed Digest Authentication no...