CVE-2022-31019 in Vapor
Summary
by MITRE • 06/09/2022
Vapor is a server-side Swift HTTP web framework. When using automatic content decoding an attacker can craft a request body that can make the server crash with the following request: `curl -d "array[_0][0][array][_0][0][array]$(for f in $(seq 1100); do echo -n '[_0][0][array]'; done)[string][_0]=hello%20world" http://localhost:8080/foo`. The issue is unbounded, attacker controlled stack growth which will at some point lead to a stack overflow and a process crash. This issue has been fixed in version 4.61.1.
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Analysis
by VulDB Data Team • 06/11/2022
The vulnerability described in CVE-2022-31019 affects Vapor, a server-side swift HTTP web framework that processes incoming HTTP requests through automatic content decoding mechanisms. This particular flaw represents a critical stack overflow condition that can be triggered by carefully crafted malicious input during request processing. The vulnerability manifests when the framework attempts to parse nested array structures within request bodies, creating an unbounded recursive parsing operation that consumes excessive stack memory.
The technical implementation of this vulnerability stems from insufficient input validation and bounds checking within Vapor's automatic content decoding system. When processing the malicious payload demonstrated in the exploit, the framework recursively parses nested array references without proper depth limits or stack growth restrictions. The crafted request body contains a repetitive pattern of array indexing that, when parsed, creates an exponential growth in stack consumption. Each recursive parsing step adds significant memory overhead to the call stack, with the example payload containing over 1100 recursive references that compound exponentially.
This vulnerability directly maps to CWE-772, which describes insufficient resource pool sizing or lack of bounds checking in recursive parsing operations. The issue represents a classic stack overflow condition where the recursive parsing mechanism lacks proper termination conditions or depth limiting, allowing an attacker to exhaust available stack memory. The attack vector operates entirely through HTTP request body manipulation, making it particularly dangerous as it requires no authentication or privileged access to exploit. The process crash occurs when the system stack overflows, causing the web server to terminate unexpectedly and potentially leading to denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited to cause persistent denial of service against Vapor applications. Attackers can repeatedly send malicious requests to crash server processes, potentially leading to application downtime and loss of service availability. The vulnerability affects any application using affected versions of Vapor framework that process HTTP request bodies through automatic content decoding, making it a widespread concern for web applications built on this platform. The issue's severity is compounded by the fact that it requires no specialized knowledge to exploit, as the attack pattern is straightforward and can be automated.
Mitigation strategies for this vulnerability involve upgrading to version 4.61.1 or later, which includes proper bounds checking and stack depth limits in the content decoding mechanism. Organizations should also implement request size limits and input validation at the application level to prevent malicious payloads from reaching the vulnerable parsing logic. Network-level protections such as rate limiting and request filtering can provide additional defense-in-depth measures. The fix addresses the root cause by implementing proper recursion depth limiting and memory usage controls, preventing the unbounded stack growth that previously enabled exploitation. System administrators should conduct thorough testing of the patched version to ensure compatibility with existing application logic while maintaining security posture against this specific class of stack overflow vulnerabilities.