CVE-2022-38751 in SnakeYAML
Summary
by MITRE • 09/05/2022
Using snakeYAML to parse untrusted YAML files may be vulnerable to Denial of Service attacks (DOS). If the parser is running on user supplied input, an attacker may supply content that causes the parser to crash by stackoverflow.
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Analysis
by VulDB Data Team • 09/05/2022
The vulnerability identified as CVE-2022-38751 represents a critical denial of service weakness within applications that utilize the snakeYAML library for parsing untrusted yaml content. This flaw specifically manifests when the yaml parser processes maliciously crafted input that triggers stack overflow conditions during the parsing operation. The vulnerability stems from inadequate input validation and memory management within the yaml parsing mechanism, creating an exploitable condition where attacker-controlled data can cause the application to consume excessive stack memory resources.
The technical implementation of this vulnerability involves the snakeYAML parser's recursive descent parsing algorithm which processes yaml structures by traversing nested data elements. When an attacker supplies yaml content containing deeply nested structures or circular references that exceed the system's stack memory limits, the parser's recursive functions continue to execute until the stack space is exhausted, resulting in a stack overflow exception that terminates the application process. This behavior aligns with CWE-674, which describes "Uncontrolled Recursion" as a weakness where recursive operations lack proper termination conditions or stack depth limits.
From an operational perspective, this vulnerability poses significant risks to applications that process user-supplied yaml data without proper sanitization or validation. Systems utilizing snakeYAML for configuration management, data import operations, or api endpoints accepting yaml payloads become immediately susceptible to denial of service attacks. Attackers can craft yaml documents with excessive nesting levels or circular references that force the application to consume memory resources rapidly, potentially leading to complete service disruption. The impact extends beyond simple application crashes to encompass broader system availability concerns, particularly in multi-tenant environments where a single malicious payload could affect multiple services.
The attack surface for this vulnerability encompasses any application framework or service that relies on snakeYAML for yaml processing, including web applications, configuration management systems, and automated deployment tools. According to ATT&CK framework category T1499, this vulnerability represents a denial of service technique that targets application availability by exploiting implementation weaknesses in parsing libraries. Organizations using vulnerable versions of snakeYAML should immediately implement input validation measures, including setting maximum nesting limits, implementing stack depth monitoring, and restricting yaml parsing to trusted sources only. Additionally, upgrading to patched versions of the library, implementing proper resource limits for parsing operations, and conducting thorough input sanitization procedures form essential defensive measures against exploitation attempts.
The root cause of this vulnerability demonstrates a fundamental flaw in how recursive parsing algorithms handle untrusted input without proper boundary checks. This weakness highlights the importance of defensive programming practices and the necessity of implementing resource constraints even within well-established parsing libraries. Organizations should consider implementing alternative parsing strategies that employ iterative approaches instead of recursive ones, or at minimum enforce strict limits on parsing depth and memory consumption to prevent exploitation of similar vulnerabilities in the future.