CVE-2026-9669

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

Products / packages Python Software Foundation CPython · Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · 3 more

Published 08/06/2026, 22:01:15 UTC

Severity and exploitation

Not in CISA KEV

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 20:55:32 UTC

PSF · CVSS:4.0 · 8.2

Assessment 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

Severity

high8.2

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Fix status not established

No structured fix or guidance is available here. Check the latest publisher advisory.

What this means

The bz2.BZ2Decompressor in Python's CPython, versions before 3.10.21, 3.11.16, 3.12.14, 3.13.14, and 3.14.6, has a stack buffer overflow weakness when reused after a decompression error, potentially crashing the process. An attacker with access to crafted input could exploit this. The impact is uncertain.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Python Software Foundation · PSF

CPython

6 ranges

PSF version evidence

Check a product version

Compare with this publisher’s ranges. This does not inspect your installation.

affected

0 → before 3.10.21

python versions

3.11.0 → before 3.11.16

python versions

3.12.0 → before 3.12.14

python versions

3.13.0 → before 3.13.14

python versions

3.14.0 → before 3.14.6

python versions

V3.1.7 → before *

custom versions

Other versions: unknown

Automatic dependency matching is unavailable for this record. Use the product evidence and publisher’s instructions to check your installation.

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

No structured fix or remediation guidance is available here. Check the full source description and vendor’s latest advisory for a patch or workaround; do not assume another version is safe.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher 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.

References

12 sources

python/cpython · pull request #150600

PatchPSF

mail.python.org/archives/list/security-announce@python.org/thread/DBJZETMGUIFK7DVUWMOXHD3Z6IX2QPSX/

Vendor advisoryPSF

python/cpython · commit 157a5df

PatchPSF

python/cpython · commit 5755d0f

PatchPSF

python/cpython · commit 619a12b

PatchPSF

python/cpython · commit d3ca269

PatchPSF

View 6 more references

python/cpython · commit 938ec03

PatchPSF

python/cpython · commit 991e6cf

PatchPSF

python/cpython · commit 1ba6135

PatchPSF

python/cpython · issues/150599

Source referencePSF

www.openwall.com/lists/oss-security/2026/06/08/17

Security advisoryCVE

cert-portal.siemens.com/productcert/html/ssa-457936.html

Source referencesiemens-SADP

Inside the record

Evidence available

Package identity · not supplied

Version evidence

Remediation guidance · not supplied

Weakness classification

Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-9669

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-121 ↗

CWE-121 Stack-based buffer overflow

PSF

Contributing organizations · 4

PSF

Assigning organization

2026-08-13

CVE

Additional data publisher

2026-06-08

CISA-ADP

Additional data publisher

2026-06-16

siemens-SADP

Additional data publisher

2026-11-10

Timeline

All times UTC

8 Jun 2026, 22:01
Advisory published
Publication date supplied by the source.
10 Nov 2026, 12:40
Source updated
Latest modification date supplied by the source.
10 Nov 2026, 12:49
Last imported by cve.new
Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes

No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.

Reading the signals

Severity · CVSS: Technical impact and attack conditions. The headline is the highest imported catalog score; sources may disagree.
Observed exploitation · KEV: An absent or unavailable KEV listing does not establish that exploitation has not occurred.
Predicted exploitation · EPSS: No EPSS estimate available in this record.

CISA-ADP · SSVC

CISA Coordinator · 2026-06-16

Exploitation: none
Automatable: no
Technical Impact: partial

SSVC describes the publisher’s decision context. Your organization’s exposure and priorities may differ.

Record identifiers

Aliases: None recorded

Source evidence

Request a correction or dispute

Start with the assigning organization for this record. Include the CVE ID, the disputed information, and supporting evidence. A dispute does not itself reject a record.

Find the responsible CNA →Official dispute and escalation process ↗

CVE CVE-2026-9669

Enrichment coverage

NVDNot fully checked

GHSANot fully checked

EUVDNot fully checked

EPSSNot fully checked

Sponsored by MoxsoBuild security habits with adaptive training and phishing simulations.View as JSON

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

Severity and exploitation

What this means

Attack conditions

Affected versions

CPython

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)

affected

unaffected

unknown

SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)

affected

unaffected

unknown

SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)

affected

unaffected

unknown

What to do

Public exploit evidence

Original source description

References

Inside the record

Evidence available

Original records

Underlying weaknesses

Timeline

Advisory published

Source updated

Last imported by cve.new

What changed