Flawfinder vs Pysa

Flawfinder is a free tool for finding possible security weaknesses in C and C++ source code. It compares source text with a built-in database of functions associated with security problems, generally disregarding comments and strings except for Flawfinder directives. Findings are ordered by risk, which depends on the function and its parameter values; the tool may reduce some false positives when it identifies a construct as not risky. Reports can be generated as text, HTML, CSV, or SARIF. The --patch option narrows findings to changed lines in a unified diff, with a one-line margin. Installation is documented through pip, source downloads, and distribution packages, and the tool requires Python 2.7 or Python 3. The project says it works on Unix-like systems, including GNU/Linux, and on Windows with Cygwin; direct Windows use has also been reported to work. Flawfinder is released under GPL-2.0+. It does not perform control-flow or data-flow analysis, so its output is an aid to review rather than a substitute for security knowledge or human judgment.

Pysa is a free, open-source Python static analysis tool that uses taint analysis to identify potential security issues. It follows data from configured sources toward dangerous sinks, such as user-controlled request data reaching an eval call. Users configure sources, sinks, features and rules in taint.config, and annotate code with .pysa model files; built-in and common Python libraries have prewritten models and rules. Sanitizer models describe data that should lose taint, including function parameters and return values. Pysa analyzes the target repository and directories in the configured search_path, but not dependency source outside that scope. When it cannot access a function’s source, it assumes the return value retains taint, which can lead to false positives. Analysis may freeze on similarly sized projects if the machine lacks enough memory. The quickstart installs it with pip install pyre-check in a Python virtual environment. Pyre supports the Language Server Protocol, and a VSCode extension connects to a running server. SAPP can ingest results for viewing and filtering in a local web UI; a GitHub Action can run Pysa in CI and show findings in GitHub’s Security code scanning UI. Pysa requires Python 3.9 or later and relies on type information from Pyrefly. The project says it can analyze codebases with millions of lines. Its repository is MIT-licensed; the Pyre repository was archived on June 26, 2026, and says Pysa moved to its own repository.