CVE-2026-9669 HIGH

CVE-2026-9669: bz2.BZ2Decompressor reuse after error can cause a stack buffer overflow

Vendor Python Software Foundation
Product CPython
Weakness CWE-121
Published June 8, 2026
Last update June 16, 2026

CVSS base score

8.2/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

June 8, 2026 CVE published
June 16, 2026 Record updated