Python CPython up to 3.15.x bz2.BZ2Decompressor stack-based overflow

CVSS Meta Temp Score
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CTI Interest Score
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3.6$0-$5k0.69

Summaryinfo

A vulnerability classified as critical has been found in Python CPython up to 3.15.x. This affects the function bz2.BZ2Decompressor. The manipulation leads to stack-based overflow. This vulnerability is referenced as CVE-2026-9669. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Python CPython up to 3.15.x. It has been rated as problematic. This issue affects the function bz2.BZ2Decompressor. The manipulation with an unknown input leads to a stack-based overflow vulnerability. Using CWE to declare the problem leads to CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). Impacted is availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-9669 since 05/27/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

Upgrading to version 3.16.0 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 3.7
VulDB Meta Temp Score: 3.6

VulDB Base Score: 3.7
VulDB Temp Score: 3.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Stack-based overflow
CWE: CWE-121 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: CPython 3.16.0
Patch: github.com

Timelineinfo

05/27/2026 CVE reserved
06/09/2026 +13 days Advisory disclosed
06/09/2026 +0 days VulDB entry created
06/09/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: 150599
Status: Confirmed

CVE: CVE-2026-9669 (🔒)
GCVE (CVE): GCVE-0-2026-9669
GCVE (VulDB): GCVE-100-369305

Entryinfo

Created: 06/09/2026 07:09
Changes: 06/09/2026 07:09 (70)
Complete: 🔍
Cache ID: 216::103

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