In the open source software (OSS) ecosystem, there exists a complex software supply chain, where developers upstream and downstream widely borrow and reuse code. This results in the widespread occurrence of recurring defects, missing fixes, and propagation issues. These are collectively referred to as cognate defects, and their scale and threats have not received extensive attention and systematic research. Software composition analysis and code clone detection methods are unable to cover the various variant issues in the supply chain scenario, while code static analysis, or static application security testing (SAST) techniques struggle to target specific defects. In this paper, we propose a novel technique for detecting cognate defects in OSS through the automatic generation of SAST rules. Specifically, it extracts key syntax and semantic information from pre- and post-patch versions of code through structural comparison and control flow to data flow analysis, and generates rules that matches these key elements. We have implemented a prototype tool called Patch2QL and applied it to fundamental OSS in C/C++. In experiments, we discovered 7 new vulnerabilities with medium to critical severity in the most popular upstream software, as well as numerous potential security issues. When analyzing downstream projects in the supply chain, we found a significant number of representative cognate defects, clarifying the threat posed by this issue. Additionally, compared to general-purpose SAST and signature-based mechanisms, the generated rules perform better at discover all variants of cognate defects.