CVE-2026-6100

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.

References

https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-6100.json

https://mail.python.org/archives/list/[email protected]/thread/HTWB2Z6KT5QQX4RYEZAFININDHNOSIF3/

https://github.com/python/cpython/pull/148396

https://github.com/python/cpython/issues/148395

https://github.com/python/cpython/commit/e20c6c9667c99ecaab96e1a2b3767082841ffc8b

https://github.com/python/cpython/commit/c3cf71c3366fe49acb776a639405c0eea6169c20

https://github.com/python/cpython/commit/8fc66aef6d7b3ae58f43f5c66f9366cc8cbbfcd2

https://github.com/python/cpython/commit/6a5f79c8d7bbf22b083b240910c7a8781a59437d

https://github.com/python/cpython/commit/47128e64f98c3a20271138a98c2922bea2a3ee0e

https://bugzilla.redhat.com/show_bug.cgi?id=2457932

https://access.redhat.com/security/cve/CVE-2026-6100

https://access.redhat.com/errata/RHSA-2026:9228

https://access.redhat.com/errata/RHSA-2026:8824

https://access.redhat.com/errata/RHSA-2026:8822

https://access.redhat.com/errata/RHSA-2026:30089

https://access.redhat.com/errata/RHSA-2026:30088

https://access.redhat.com/errata/RHSA-2026:30087

https://access.redhat.com/errata/RHSA-2026:30078

https://access.redhat.com/errata/RHSA-2026:26187

https://access.redhat.com/errata/RHSA-2026:25096

https://access.redhat.com/errata/RHSA-2026:21682

https://access.redhat.com/errata/RHSA-2026:21275

https://access.redhat.com/errata/RHSA-2026:19590

https://access.redhat.com/errata/RHSA-2026:19576

https://access.redhat.com/errata/RHSA-2026:19571

https://access.redhat.com/errata/RHSA-2026:19570

https://access.redhat.com/errata/RHSA-2026:19549

https://access.redhat.com/errata/RHSA-2026:19216

https://access.redhat.com/errata/RHSA-2026:19177

https://access.redhat.com/errata/RHSA-2026:19176

https://access.redhat.com/errata/RHSA-2026:19175

https://access.redhat.com/errata/RHSA-2026:19064

https://access.redhat.com/errata/RHSA-2026:19019

https://access.redhat.com/errata/RHSA-2026:17619

https://access.redhat.com/errata/RHSA-2026:17525

https://access.redhat.com/errata/RHSA-2026:16699

https://access.redhat.com/errata/RHSA-2026:14656

https://access.redhat.com/errata/RHSA-2026:14653

https://access.redhat.com/errata/RHSA-2026:14652

https://access.redhat.com/errata/RHSA-2026:13812

https://access.redhat.com/errata/RHSA-2026:13692

https://access.redhat.com/errata/RHSA-2026:11768

https://access.redhat.com/errata/RHSA-2026:11077

https://access.redhat.com/errata/RHSA-2026:11062

https://access.redhat.com/errata/RHSA-2026:10950

https://access.redhat.com/errata/RHSA-2026:10949

https://access.redhat.com/errata/RHSA-2026:10774

https://access.redhat.com/errata/RHSA-2026:10745

https://access.redhat.com/errata/RHSA-2026:10711

https://access.redhat.com/errata/RHSA-2026:10141

https://access.redhat.com/errata/RHSA-2026:10140

https://access.redhat.com/errata/RHSA-2026:10117

http://www.openwall.com/lists/oss-security/2026/04/13/10

Details

Source: Mitre, NVD

Risk Information

CVSS v2

CVSS v3

CVSS v4

EPSS