CVE-2026-6100Use-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-u…
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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.
- CVSS
- 8.1 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-416, CWE-787, CWE-825
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Awaiting Analysis
- Record last updated
- Aug 13, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
No affected products are listed yet.
References
- https://github.com/python/cpython/commit/47128e64f98c3a20271138a98c2922bea2a3ee0e
- https://github.com/python/cpython/commit/6a5f79c8d7bbf22b083b240910c7a8781a59437d
- https://github.com/python/cpython/commit/8fc66aef6d7b3ae58f43f5c66f9366cc8cbbfcd2
- https://github.com/python/cpython/commit/c3cf71c3366fe49acb776a639405c0eea6169c20
- https://github.com/python/cpython/commit/e20c6c9667c99ecaab96e1a2b3767082841ffc8b
- https://github.com/python/cpython/commit/ea8d735eb084cf8cc021df1a30e90d10a8f052e3
- https://github.com/python/cpython/issues/148395
- https://github.com/python/cpython/pull/148396
- https://mail.python.org/archives/list/security-announce@python.org/thread/HTWB2Z6KT5QQX4RYEZAFININDHNOSIF3/
- http://www.openwall.com/lists/oss-security/2026/04/13/10
- https://access.redhat.com/errata/RHSA-2026:10117
- https://access.redhat.com/errata/RHSA-2026:10140
- https://access.redhat.com/errata/RHSA-2026:10141
- https://access.redhat.com/errata/RHSA-2026:10711
- https://access.redhat.com/errata/RHSA-2026:10745
- https://access.redhat.com/errata/RHSA-2026:10774
- https://access.redhat.com/errata/RHSA-2026:10949
- https://access.redhat.com/errata/RHSA-2026:10950
- https://access.redhat.com/errata/RHSA-2026:11062
- https://access.redhat.com/errata/RHSA-2026:11077
- https://access.redhat.com/errata/RHSA-2026:11768
- https://access.redhat.com/errata/RHSA-2026:13692
- https://access.redhat.com/errata/RHSA-2026:13812
- https://access.redhat.com/errata/RHSA-2026:14652
- https://access.redhat.com/errata/RHSA-2026:14653
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.