CVE-2026-15310: zipfile: bzip2/LZMA/Zstandard members decompress without a max_length bound, defeating chunked-read memory limits
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
Other sources
zipfile: bzip2/LZMA/Zstandard members decompress without a maxlength bound, defeating chunked-read memory limits
— Microsoft
Affected Software
Event History
Frequently Asked Questions
What conditions are required for exploitation?
An application must decompress a crafted ZIP file containing members compressed with bzip2, LZMA, or Zstandard. The attacker-controlled size can cause Python to pre-allocate memory and potentially exhaust available memory.
Are applications protected by reading ZIP members in chunks?
Not reliably for ZIP members using bzip2, LZMA, or Zstandard compression. These decompression paths lack a max_length bound, so crafted member data can defeat chunked-read memory limits.
What is the likely operational impact?
The stated impact is memory exhaustion. Affected processes may consume excessive memory while decompressing a malicious ZIP file.