MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment, or extra field. NOTE: MiniZip is not a supported part of the zlib product. NOTE: pyminizip through 0.2.6 is also vulnerable because it bundles an affected zlib version, and exposes the applicable MiniZip code through its compress API.

zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. NOTE: only applications that call inflateGetHeader are affected. Some common applications bundle the affected zlib source code but may be unable to call inflateGetHeader (e.g., see the nodejs/node reference).

zlib before 1.2.12 allows memory corruption when deflating (i.e., when compressing) if the input has many distant matches.

The decompression algorithm in zlib 1.1.3 and earlier, as used in many different utilities and packages, causes inflateEnd to release certain memory more than once (a "double free"), which may allow local and remote attackers to execute arbitrary code via a block of malformed compression data.