-------- Forwarded Message -------- Subject: [Security-announce][CVE-2026-6100] Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure Date: Mon, 13 Apr 2026 17:13:40 +0000 From: Seth Larson <[email protected]> Reply-To: [email protected] To: [email protected] There is a CRITICAL severity vulnerability affecting CPython. Use-after-free (UAF) was possible in the `lzma.LZMADecompressor`, `bz2.BZ2Decompressor`, and `gzip.GzipFile` when a memory allocation fails with a `MemoryError` and the decompression instance is re-used. This scenario can be triggered if the process is under memory pressure. The fix cleans up the dangling pointer in this specific error condition. The vulnerability is only present if the program re-uses decompressor instances across multiple decompression calls even after a `MemoryError` is raised during decompression. Using the helper functions to one-shot decompress data such as `lzma.decompress()`, `bz2.decompress()`, `gzip.decompress()`, and `zlib.decompress()` are not affected as a new decompressor instance is created for each call. If the decompressor instance is not re-used after an error condition, this usage is similarly not vulnerable. Please see the linked CVE ID for the latest information on affected versions: * https://www.cve.org/CVERecord?id=CVE-2026-6100 * https://github.com/python/cpython/pull/148396 _______________________________________________ Security-announce mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/security-announce.python.org
