CVE-2022-40468 in Tinyproxy
Summary
by MITRE • 09/19/2022
Potential leak of left-over heap data if custom error page templates containing special non-standard variables are used. Tinyproxy commit 84f203f and earlier use uninitialized buffers in process_request() function.
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Analysis
by VulDB Data Team • 11/05/2025
CVE-2022-40468 represents a heap data leakage vulnerability affecting Tinyproxy versions up to and including commit 84f203f. This vulnerability arises from the improper handling of uninitialized memory buffers within the process_request() function when processing custom error page templates that contain special non-standard variables. The flaw occurs during the proxy server's request processing lifecycle where memory allocated for error page rendering is not properly initialized before use, potentially exposing sensitive data remnants from previous heap allocations.
The technical implementation of this vulnerability stems from inadequate memory management practices within Tinyproxy's error handling mechanism. When custom error templates are processed, the software fails to initialize buffer memory areas that store template variable data, leading to the accidental exposure of previously allocated heap memory contents. This uninitialized buffer behavior creates a classic information disclosure vulnerability where residual data from prior operations may be inadvertently included in the rendered error response. The vulnerability is particularly concerning because it can potentially expose sensitive information such as authentication tokens, session data, or other confidential content that was previously stored in the same memory regions.
From an operational impact perspective, this vulnerability poses significant security risks to organizations relying on Tinyproxy for web proxy services. Attackers could exploit this weakness to extract sensitive information from memory dumps or by crafting specific error conditions that trigger the vulnerable code path. The exposure of left-over heap data could potentially lead to credential theft, session hijacking, or other advanced persistent threats depending on what sensitive information was previously stored in the affected memory regions. This vulnerability aligns with CWE-119, which addresses improper access to memory buffers, and specifically relates to improper initialization of memory buffers as outlined in CWE-457.
The attack surface for this vulnerability is primarily limited to scenarios where custom error page templates are utilized within Tinyproxy configurations, particularly when these templates contain special non-standard variables. According to ATT&CK framework, this vulnerability maps to T1566.001, which covers credential access through the exploitation of software vulnerabilities, and potentially T1005, which involves data from local systems. The exploitation requires the attacker to configure or influence the proxy server to use custom error templates with special variables, making it moderately difficult to exploit in environments with strict configuration controls but relatively straightforward in poorly configured systems.
Mitigation strategies for CVE-2022-40468 should focus on updating Tinyproxy to versions that have addressed this uninitialized buffer issue through proper memory initialization practices. Organizations should also implement strict controls over custom error template configurations and conduct regular security audits of proxy server configurations. The fix typically involves ensuring that all buffer memory areas are properly initialized before processing template variables, which aligns with secure coding practices recommended in the OWASP Secure Coding Guidelines. Additionally, monitoring for unusual error response patterns and implementing memory sanitization techniques can help detect potential exploitation attempts while maintaining operational security posture.