Vulnerability Detection 2022 - The increasing number of software vulnerabilities pose serious security attacks and lead to system compromise, information leakage or denial of service. It is a challenge to further improve the vulnerability detection technique. Nowadays most applications are implemented using C/C++. In this paper we focus on the detection of overflow vulnerabilities in C/C++ source code. A novel scheme named VulMiningBGS (Vulnerability Mining Based on Graph Similarity) is proposed. We convert the source code into Top N-Weighted Range Sum Feature Graph (TN-WRSFG), and graph similarity comparisons based on source code level can be effectively carried on to detect possible vulnerabilities. Three categories of vulnerabilities in the Juliet test suite are used, i.e., CWE121, CWE122 and CWE190, with four indicators for performance evaluation (precision, recall, accuracy and F1\_score). Experimental results show that our scheme outperforms the traditional methods, and is effective in the overflow vulnerability detection for C/C++ source code.