xz is a pure golang package for reading and writing xz-compressed files. Prior to version 0.5.14, it is possible to put data in front of an LZMA-encoded byte stream without detecting the situation while reading the header. This can lead to increased memory consumption because the current implementation allocates the full decoding buffer directly after reading the header. The LZMA header doesn't include a magic number or has a checksum to detect such an issue according to the specification. Note that the code recognizes the issue later while reading the stream, but at this time the memory allocation has already been done. This issue has been patched in version 0.5.14.

XZ Utils provide a general-purpose data-compression library plus command-line tools. In XZ Utils 5.3.3alpha to 5.8.0, the multithreaded .xz decoder in liblzma has a bug where invalid input can at least result in a crash. The effects include heap use after free and writing to an address based on the null pointer plus an offset. Applications and libraries that use the lzma_stream_decoder_mt function are affected. The bug has been fixed in XZ Utils 5.8.1, and the fix has been committed to the v5.4, v5.6, v5.8, and master branches in the xz Git repository. No new release packages will be made from the old stable branches, but a standalone patch is available that applies to all affected releases.

XZ Utils provide a general-purpose data-compression library plus command-line tools. When built for native Windows (MinGW-w64 or MSVC), the command line tools from XZ Utils 5.6.2 and older have a command line argument injection vulnerability. If a command line contains Unicode characters (for example, filenames) that don't exist in the current legacy code page, the characters are converted to similar-looking characters with best-fit mapping. Some best-fit mappings result in ASCII characters that change the meaning of the command line, which can be exploited with malicious filenames to do argument injection or directory traversal attacks. This vulnerability is fixed in 5.6.3. Command line tools built for Cygwin or MSYS2 are unaffected. liblzma is unaffected.