Hi! Brotli 1.0.9 contains a security update, which fixes an "integer overflow" problem [1]. Please update it. A cygport file for updating is placed at https://github.com/cygwin-lem/brotli-cygport/tree/n_1.0.9-1 . Test packages generated from it are placed at https://cygwin-lem.github.io/brotli-cygport/ , or https://github.com/cygwin-lem/brotli-cygport/tree/n_1.0.9-1_gh-pages . But the cygport file is not tested under Cygwin CI AppVeyor, yet. So BUILD_REQUIRES in brotli.cygport might be insufficient. [1]: https://github.com/google/brotli/blob/master/README.md Regards, Lem