CVE-2017-11692 in yaml-cpp
Summary
by MITRE
The function "Token& Scanner::peek" in scanner.cpp in yaml-cpp 0.5.3 and earlier allows remote attackers to cause a denial of service (assertion failure and application exit) via a '!2' string.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-11692 resides within the yaml-cpp library version 0.5.3 and earlier, specifically in the Token& Scanner::peek function located in scanner.cpp. This flaw represents a classic denial of service vulnerability that can be exploited by remote attackers to disrupt application functionality through crafted input. The vulnerability manifests when the scanner encounters a '!2' string sequence, triggering an assertion failure that causes the application to terminate unexpectedly.
The technical root cause of this vulnerability stems from inadequate input validation within the YAML parsing mechanism. When the scanner processes the '!2' string, it fails to properly handle this specific token sequence, leading to an assertion failure within the parsing logic. This assertion failure occurs because the scanner's peek function does not adequately validate the token structure before attempting to process it, resulting in a program crash. The vulnerability is particularly concerning as it can be triggered through external input, making it exploitable in networked environments where yaml-cpp is used to parse user-supplied YAML data.
From an operational impact perspective, this vulnerability creates significant risks for applications that rely on yaml-cpp for configuration parsing, data serialization, or content management. When exploited, the denial of service condition can cause applications to crash repeatedly, leading to service unavailability and potential business disruption. The vulnerability affects any system where yaml-cpp is integrated, including web applications, configuration management tools, and any software that processes YAML formatted data from untrusted sources. The ease of exploitation through simple string injection makes this vulnerability particularly dangerous in production environments.
The vulnerability aligns with CWE-617, which addresses reachable assertions, and demonstrates characteristics consistent with the ATT&CK technique T1499.1, specifically Denial of Service through resource exhaustion. Organizations utilizing yaml-cpp should prioritize immediate patching to version 0.5.4 or later, which contains the necessary fixes for this vulnerability. Additionally, implementing input validation measures and sanitization routines can provide additional defense-in-depth protection against similar vulnerabilities. Security teams should also consider monitoring for exploitation attempts and implementing proper error handling to prevent cascading failures when such vulnerabilities are present in their systems.
This vulnerability serves as a reminder of the importance of robust input validation in parsing libraries and highlights the critical need for thorough testing of edge cases in configuration and data processing components. The impact extends beyond simple application crashes, potentially affecting system availability and user experience in applications where YAML parsing is a core functionality.