CVE-2011-1843 in Tinyproxy
Summary
by MITRE
Integer overflow in conf.c in Tinyproxy before 1.8.3 might allow remote attackers to bypass intended access restrictions in opportunistic circumstances via a TCP connection, related to improper handling of invalid port numbers.
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Analysis
by VulDB Data Team • 11/05/2021
The vulnerability identified as CVE-2011-1843 represents a critical integer overflow flaw within the Tinyproxy HTTP proxy server software. This issue affects versions prior to 1.8.3 and stems from improper validation of port numbers during TCP connection handling. The vulnerability resides in the conf.c configuration file where the software fails to properly manage integer arithmetic when processing invalid port specifications. When an attacker crafts a malicious TCP connection request with an malformed port number, the integer overflow condition can occur during the parsing and validation process. This flaw creates a scenario where the software's access control mechanisms may be circumvented under specific opportunistic conditions, allowing unauthorized access to proxy resources that should otherwise be restricted. The vulnerability demonstrates a classic security weakness in input validation and arithmetic handling that can have significant implications for network security.
The technical implementation of this vulnerability involves the manipulation of integer variables during port number processing within Tinyproxy's configuration parsing logic. When the software encounters an invalid port number, the arithmetic operations used to validate or process these values can result in integer overflow conditions. This overflow typically occurs when the software attempts to perform mathematical operations on port values that exceed the maximum representable value for the integer type being used. The resulting overflow can cause the validation logic to produce incorrect results, effectively bypassing the intended access control checks that are meant to prevent unauthorized connections. This type of flaw falls under the CWE-190 category of Integer Overflow or Wraparound, which is a well-documented vulnerability pattern in software security. The improper handling of integer arithmetic in network protocol implementations creates opportunities for attackers to manipulate system behavior through carefully crafted inputs.
The operational impact of CVE-2011-1843 extends beyond simple access bypass to potentially enable more sophisticated attacks within network environments. When an integer overflow occurs during TCP connection processing, attackers can exploit this condition to circumvent proxy access controls and gain unauthorized access to internal network resources that the proxy is designed to protect. This vulnerability is particularly concerning in environments where Tinyproxy serves as a gateway between internal and external networks, as it could allow attackers to bypass filtering mechanisms and access restricted services. The opportunistic nature of this vulnerability means that exploitation may not require highly sophisticated techniques, but rather relies on the predictable behavior of integer overflow conditions in specific software implementations. Organizations using vulnerable versions of Tinyproxy face risks of unauthorized data access, potential network reconnaissance, and possible lateral movement within their network infrastructure. The vulnerability's impact aligns with ATT&CK technique T1071.004 for application layer protocol manipulation and T1046 for network service scanning.
Mitigation strategies for CVE-2011-1843 primarily focus on upgrading to patched versions of Tinyproxy software. System administrators should immediately update to Tinyproxy version 1.8.3 or later, where the integer overflow vulnerability has been addressed through proper input validation and arithmetic handling. Additionally, implementing network-level restrictions such as firewall rules to limit access to the proxy server and monitoring for unusual connection patterns can provide additional defense-in-depth measures. The fix typically involves strengthening the port number validation logic to prevent integer overflow conditions during arithmetic operations and ensuring proper bounds checking for all integer values used in connection processing. Organizations should also consider implementing network segmentation and access control policies that reduce the potential impact of such vulnerabilities. Regular security assessments and vulnerability scanning should include checks for outdated proxy software versions to prevent similar issues from arising in the future. The remediation process should also include reviewing and updating security configurations to ensure that proxy services operate with minimal privileges and appropriate access controls in place.