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CVE-2026-6100— Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure

Quick assessment

Affected
Python Software Foundation CPython
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Python是Python基金会的一套开源的、面向对象的程序设计语言。该语言具有可扩展、支持模块和包、支持多种平台等特点。 Python存在安全漏洞，该漏洞源于内存分配失败时重用解压缩实例可能导致释放后重用。

CVSS 9.1 · Critical EPSS 0.76% · P54

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 6

VendorProduct Version RangeStatus
Python Software Foundation CPython < 3.10.21 affected
3.11.0< 3.11.16 affected
3.12.0< 3.12.14 affected
3.13.0< 3.13.14 affected
3.14.0a1< 3.14.5rc1 affected
3.15.0a1< 3.15.0b1 affected
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I. Basic Information for CVE-2026-6100

Vulnerability Information
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Vulnerability Title
Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
Python 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Python是Python基金会的一套开源的、面向对象的程序设计语言。该语言具有可扩展、支持模块和包、支持多种平台等特点。 Python存在安全漏洞，该漏洞源于内存分配失败时重用解压缩实例可能导致释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Python Software Foundation CPython 0 ~ 3.10.21 -

II. Public POCs for CVE-2026-6100

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 11410 chars
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III. Intelligence Information for CVE-2026-6100

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Patches & Fixes for CVE-2026-6100 (4)

Vendor Advisories for CVE-2026-6100 (1)

IV. Related Vulnerabilities

Same product: CPython
Same vendor: Python Software Foundation
Same weakness: CWE-416

V. Comments for CVE-2026-6100

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