High severity · published Jun 8, 2026
CVE-2026-9669
bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow
8.2
CVSS
0.4%
EPSS
No
On KEV
Description
bz2.BZ2Decompressor objects could be reused after a decompression error. If an application caught the resulting OSError and retried with the same decompressor, crafted input could cause the decompressor to resume from an invalid internal state and perform out-of-bounds writes to a stack buffer. This could crash the process when processing untrusted data.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CP
CPython · Python Software Foundation
before 3.10.21; 3.11.0 before 3.11.16; 3.12.0 before 3.12.14; 3.13.0 before 3.13.14; 3.14.0 before 3.14.6; 3.15.0a1 before 3.15.0b3 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9669
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-9669
github.com
https://github.com/python/cpython/commit/157a5df8cb5d82b33f918a7489e72ce95ceb12b6
github.com
https://github.com/python/cpython/commit/1ba6135eae75ad8413413caeeedb56ae72320636
github.com
https://github.com/python/cpython/commit/5755d0f083949ff3c5bf3a37e673e24e306b036e
github.com
https://github.com/python/cpython/commit/619a12b2e545391dc436b3af79dda22337382a6f
github.com
https://github.com/python/cpython/commit/938ec030e90c5e53f1faac6fab1643f14e4f4a79
github.com
https://github.com/python/cpython/commit/991e6cf86496718c4ef00b362d640e00cb5c85b2
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