Web applications are attractive attack targets given their popularity and large number of vulnerabilities. To mitigate the threat of web vulnerabilities, an important piece of information is their affected versions. However, it is non-trivial to build accurate affected version information because confirming a version as affected or unaffected requires security expertise and huge efforts, while there are usually hundreds of versions to examine. As a result, such information is maintained in a low-quality manner in almost every public vulnerability database. Therefore, it is extremely useful to have a tool that can automatically and precisely examine a large part (even if not all) of the software versions as affected or unaffected.

To this end, this paper proposes a vulnerability-centric approach for precise (un)affected version analysis for web vulnerabilities. The key idea is to extract the vulnerability logic from a patch and directly use the vulnerability logic to check whether a version is (un)affected or not. Compared with existing works, our vulnerability-centric approach helps to tolerate the code changes across different software versions. We construct a high-quality dataset with 34 CVEs and 299 software versions to evaluate our approach. The results show that our approach achieves a precision of 98.15% and a recall of 85.01% in identifying (un)affected versions and significantly outperforms existing tools (e.g., V-SZZ, ReDebug, V0Finder).