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CVE-2026-9669

bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow

HIGH
8.2
CVSS Score
Published: June 8, 2026 at 10:01 PM UTC
Updated: August 13, 2026 at 01:16 AM UTC
1 product affected across 1 vendorPython

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Severity
HIGH8.2
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Python· Python
60%
v < 3.10.213.11.0 ≤ v < 3.11.163.12.0 ≤ v < 3.12.143.13.0 ≤ v < 3.13.143.14.0 ≤ v < 3.14.63.15.0a1 ≤ v < 3.15.0b33.11.03.12.03.13.03.14.03.15.0a1
Affected range stops below 3.10.21, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.11.16, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.12.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.13.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.14.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.15.0b3, so it looks safe — our inference, not a vendor statement

References (11)

Patch
Source: cverecord
https://github.com/python/cpython/pull/150600
Vendor Advisory
Source: cverecord
https://mail.python.org/archives/list/[email protected]/thread/DBJZETMGUIFK7DVUWMOXHD3Z6IX2QPSX/
Issue Tracking
Source: cverecord
https://github.com/python/cpython/issues/150599
Source: af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2026/06/08/17
Patch
Source: [email protected]
https://github.com/python/cpython/commit/157a5df8cb5d82b33f918a7489e72ce95ceb12b6
Patch
Source: [email protected]
https://github.com/python/cpython/commit/5755d0f083949ff3c5bf3a37e673e24e306b036e
Patch
Source: [email protected]
https://github.com/python/cpython/commit/619a12b2e545391dc436b3af79dda22337382a6f
Patch
Source: [email protected]
https://github.com/python/cpython/commit/d3ca26983dfbccdf609f24ff5877dc3118e4702d

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGHPSF
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-121

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