CVE-2009-2622 in Squid
Summary
by MITRE
Squid 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11 allows remote attackers to cause a denial of service via malformed requests including (1) "missing or mismatched protocol identifier," (2) missing or negative status value," (3) "missing version," or (4) "missing or invalid status number," related to (a) HttpMsg.cc and (b) HttpReply.cc.
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Analysis
by VulDB Data Team • 08/13/2021
The vulnerability identified as CVE-2009-2622 represents a critical denial of service flaw within the Squid web proxy software ecosystem. This vulnerability affects versions 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11, exposing a fundamental parsing weakness in how the software handles malformed HTTP requests. The issue stems from inadequate input validation mechanisms within the HttpMsg.cc and HttpReply.cc source code modules, which are responsible for processing HTTP message structures and reply formatting respectively. These components fail to properly validate the integrity of incoming HTTP protocol identifiers, status values, and version information, creating exploitable conditions that can be leveraged by remote attackers to disrupt service availability.
The technical exploitation of this vulnerability occurs through carefully crafted malformed HTTP requests that manipulate specific protocol elements including missing or mismatched protocol identifiers, negative or missing status values, missing version information, and invalid status numbers. These malformed requests exploit the software's failure to implement proper bounds checking and validation routines when processing HTTP message headers and status codes. The vulnerability manifests as a failure in the HTTP message parsing logic where the system attempts to process incomplete or malformed data structures without adequate error handling or recovery mechanisms. This results in the proxy service becoming unresponsive or crashing entirely, effectively rendering the proxy unavailable to legitimate users and creating a denial of service condition that can be exploited at scale.
From an operational impact perspective, this vulnerability poses significant risks to organizations relying on Squid as their primary web proxy solution. The remote nature of the attack means that malicious actors can exploit this weakness from outside the network perimeter without requiring authentication or privileged access. The service disruption can affect thousands of users simultaneously, particularly in large enterprise environments where Squid serves as a central caching and proxy server. The vulnerability aligns with CWE-129, which addresses improper validation of array indices and buffer overflows, and more specifically with CWE-122, which covers buffer overflow conditions in input validation. The attack vectors described in this vulnerability map directly to techniques found in the MITRE ATT&CK framework under the T1499 category, specifically targeting network denial of service through protocol manipulation.
Organizations should implement immediate mitigations including upgrading to patched versions of Squid software, which address the core parsing vulnerabilities in HttpMsg.cc and HttpReply.cc modules. Network-level protections such as intrusion detection systems can help identify and block malformed traffic patterns associated with this exploit. Additionally, implementing rate limiting and connection throttling mechanisms can reduce the effectiveness of denial of service attempts. The vulnerability highlights the importance of robust input validation and proper error handling in network services, particularly those handling untrusted HTTP traffic. Security teams should also consider implementing application firewalls or web application firewalls that can detect and filter malformed HTTP requests before they reach the Squid proxy server, providing an additional layer of protection against similar protocol-based attacks.