EUVD-2026-22028
CVSS VectorNVD
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionNVD
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.
AnalysisAI
CPython decompression modules (lzma, bz2, gzip) allow memory corruption via use-after-free when decompressor instances are reused after MemoryError exceptions under memory pressure. Affects all CPython versions before 3.15.0. …
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RemediationAI
Within 24 hours: Inventory all Python services and applications using lzma, bz2, or gzip modules; identify those processing network-supplied compressed data. Within 7 days: Test and deploy CPython 3.15.0 to development and staging environments; validate application compatibility. …
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