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CVE-2026-9669· NVD / CVE Program· CNA PSF

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

Noroxi assessment

Priority: Monitor (action score 32/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.42% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Python Software Foundation CPython 3.10.21, 3.11.16, 3.12.14; azl3 python3 3.12.9-14 on Azure Linux 3.0 3.12.9-14.

Low priority for now. Upgrade to Python Software Foundation CPython 3.10.21, 3.11.16, 3.12.14; azl3 python3 3.12.9-14 on Azure Linux 3.0 3.12.9-14 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

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.

HighCVSS 8.2 · v4.0—No exploit Fix available
Published
Jun 8, 2026
Updated
Aug 13, 2026
EPSS
0.4% · 35th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · PSF
8.2
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-9669

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (PSF). Independent of NVD's CPE analysis and usually ahead of it.

  • Python Software Foundation CPython

    • before 3.10.21affected · python
    • 3.11.0 and later · before 3.11.16affected · python
    • 3.12.0 and later · before 3.12.14affected · python
    • 3.13.0 and later · before 3.13.14affected · python
    • 3.14.0 and later · before 3.14.6affected · python
    • 3.15.0a1 and later · before 3.15.0b3affected · python

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.24python3before 3.14.7-r03.14.7-r0
Debian:12python3.11before 3.11.2-6+deb12u93.11.2-6+deb12u9
Debian:13python3.13before 3.13.5-2+deb13u33.13.5-2+deb13u3
Debian:14python3.13before 3.13.14-13.13.14-1
Debian:14python3.14before 3.14.6-13.14.6-1
openSUSE:Tumbleweedpython310before 3.10.21-1.13.10.21-1.1
openSUSE:Tumbleweedpython311before 3.11.16-1.13.11.16-1.1
openSUSE:Tumbleweedpython312before 3.12.14-1.13.12.14-1.1
openSUSE:Tumbleweedpython313before 3.13.15-1.13.13.15-1.1
openSUSE:Tumbleweedpython314before 3.14.6-1.13.14.6-1.1
openSUSE:Tumbleweedpython315before 3.15.0~rc2-1.13.15.0~rc2-1.1
Red Hat:hummingbird:1python-unversioned-commandbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3before 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-debugbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-develbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-idlebefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-libsbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-testbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3-tkinterbefore 0:3.14.7-1.2.hum10:3.14.7-1.2.hum1
Red Hat:hummingbird:1python3.10before 0:3.10.21-1.3.hum10:3.10.21-1.3.hum1
Red Hat:hummingbird:1python3.10-debugbefore 0:3.10.21-1.3.hum10:3.10.21-1.3.hum1
Red Hat:hummingbird:1python3.10-develbefore 0:3.10.21-1.3.hum10:3.10.21-1.3.hum1
Red Hat:hummingbird:1python3.10-idlebefore 0:3.10.21-1.3.hum10:3.10.21-1.3.hum1
Red Hat:hummingbird:1python3.10-libsbefore 0:3.10.21-1.3.hum10:3.10.21-1.3.hum1

+42

Same product

python software foundation: all records

Other highest-scoring records for the same primary product.

  • CVE-2025-4517Arbitrary writes via tarfile realpath overflow
    37Monitor
  • CVE-2026-19445Use-after-free of a server-side SSLContext when sni_callback switches contexts
    36Monitor
  • CVE-2026-6100Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure
    36Monitor
  • CVE-2026-3298Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes
    35Monitor
  • CVE-2024-12254Unbounded memory buffering in SelectorSocketTransport.writelines()
    35Monitor
  • CVE-2024-8088Infinite loop when iterating over zip archive entry names from zipfile.Path
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Python Software Foundation CPython3.10.21Vendor (CNA)
Python Software Foundation CPython3.11.16Vendor (CNA)
Python Software Foundation CPython3.12.14Vendor (CNA)
Python Software Foundation CPython3.13.14Vendor (CNA)
Python Software Foundation CPython3.14.6Vendor (CNA)
Python Software Foundation CPython3.15.0b3Vendor (CNA)
azl3 python3 3.12.9-14 on Azure Linux 3.03.12.9-14 · CBL-Mariner ReleasesMicrosoft (MSRC)
alpine:python33.14.7-r0 · Alpine:v3.24Package registry (OSV)
debian:python3.113.11.2-6+deb12u9 · Debian:12Package registry (OSV)
debian:python3.133.13.5-2+deb13u3 · Debian:13Package registry (OSV)
debian:python3.143.14.6-1 · Debian:14Package registry (OSV)
opensuse:python3103.10.21-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3113.11.16-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3123.12.14-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3133.13.15-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3143.14.6-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:python3153.15.0~rc2-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:python-unversioned-command0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python30:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-debug0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-devel0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-idle0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-libs0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-test0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3-tkinter0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3.140:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3.14-freethreading0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3.14-freethreading-debug0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:python3.14-freethreading-devel0:3.14.7-1.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
suse:python2.7.18-150000.133.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7Package registry (OSV)

+6

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-571355 days apartOut-of-bounds read/write during remote profiling and asyncio process introspection when connecting to malicious target
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-121 · Stack-based Buffer Overflow

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (10 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records