CVE-2026-6100

Summary

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 used per call. If the decompressor instance is not re-used after an error condition, this usage is similarly not vulnerable.

Affected Software

VendorProductVersion RangeStatus
Python Software FoundationCPython0 < 3.10.21affected
Python Software FoundationCPython3.11.0 < 3.11.16affected
Python Software FoundationCPython3.12.0 < 3.12.14affected
Python Software FoundationCPython3.13.0 < 3.13.14affected
Python Software FoundationCPython3.14.0a1 < 3.14.5rc1affected
Python Software FoundationCPython3.15.0a1 < 3.15.0b1affected

Weaknesses

  • CWE-416: CWE-416 Use after free
  • CWE-787: CWE-787 Out-of-bounds write

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

CVE Program Container

Additional References

python: Python: Arbitrary code execution or information disclosure via use-after-free in decompression modules

Additional References

References