NVD / CVE Program· CNA PSF

CVE-2024-12254: Unbounded memory buffering in SelectorSocketTransport.writelines()

HighCVSS 8.7 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 35/100)

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: 1.8% (FIRST EPSS); higher than 79.6% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: Python Software Foundation CPython 3.12.9, 3.13.2, 3.14.0a3; azl3 python3 3.12.3-5 on Azure Linux 3.0 3.12.3-5.

Low priority for now. Upgrade to Python Software Foundation CPython 3.12.9, 3.13.2, 3.14.0a3; azl3 python3 3.12.3-5 on Azure Linux 3.0 3.12.3-5 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

Primary sources: NVD · CVE.org · FIRST EPSS

Starting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines() method would not "pause" writing and signal to the Protocol to drain the buffer to the wire once the write buffer reached the "high-water mark". Because of this, Protocols would not periodically drain the write buffer potentially leading to memory exhaustion. This vulnerability likely impacts a small number of users, you must be using Python 3.12.0 or later, on macOS or Linux, using the asyncio module with protocols, and using .writelines() method which had new zero-copy-on-write behavior in Python 3.12.0 and later. If not all of these factors are true then your usage of Python is unaffected.

Published: Dec 6, 2024
Updated: Jul 31, 2026
EPSS: 1.8% · 79th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 34 / 40 · 8.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 1.8%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · PSF: 8.7; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/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.

Is your version affected? Check it

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.

Vendor	Product	CPE
python software foundation	cpython	cpe:2.3:a:python_software_foundation:cpython

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 3.12.9affected · python
- 3.13.0 and later · before 3.13.2affected · python
- 3.14.0a1 and later · before 3.14.0a3affected · python

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
AlmaLinux:8	python3.12	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-debug	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-devel	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-idle	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-libs	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-rpm-macros	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-test	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:8	python3.12-tkinter	before 3.12.8-1.el8_10	3.12.8-1.el8_10
AlmaLinux:9	python3.12	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-debug	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-devel	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-idle	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-libs	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-test	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
AlmaLinux:9	python3.12-tkinter	before 3.12.5-2.el9_5.2	3.12.5-2.el9_5.2
Alpine:v3.20	python3	before 3.12.8-r1	3.12.8-r1
Debian:13	python3.13	before 3.13.1-2	3.13.1-2
openSUSE:Leap 15.6	python312	before 3.12.9-150600.3.18.1	3.12.9-150600.3.18.1
openSUSE:Leap 15.6	python312	before 3.12.8-150600.3.12.1	3.12.8-150600.3.12.1
openSUSE:Leap 15.6	python312-core	before 3.12.9-150600.3.18.1	3.12.9-150600.3.18.1
openSUSE:Leap 15.6	python312-core	before 3.12.8-150600.3.12.1	3.12.8-150600.3.12.1
openSUSE:Leap 15.6	python312-documentation	before 3.12.8-150600.3.12.1	3.12.8-150600.3.12.1
openSUSE:Leap 15.6	python312-documentation	before 3.12.9-150600.3.18.1	3.12.9-150600.3.18.1
openSUSE:Tumbleweed	python-aiohttp	before 3.11.16-1.1	3.11.16-1.1

+49

Same product

python software foundation: all records

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Published before and after this one in the same product

← EarlierCVE-2024-8088Aug 22, 2024 · Infinite loop when iterating over zip archive entry names from zipfile.Path
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← EarlierCVE-2024-11168Nov 12, 2024 · Improper validation of IPv6 and IPvFuture addresses
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Later →CVE-2025-0938Jan 31, 2025 · URL parser allowed square brackets in domain names
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Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
Python Software Foundation CPython	3.12.9	Vendor (CNA)
Python Software Foundation CPython	3.13.2	Vendor (CNA)
Python Software Foundation CPython	3.14.0a3	Vendor (CNA)
azl3 python3 3.12.3-5 on Azure Linux 3.0	3.12.3-5 · CBL-Mariner Releases	Microsoft (MSRC)
almalinux:python3.12	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-debug	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-devel	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-idle	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-libs	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-rpm-macros	3.12.8-1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:python3.12-test	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
almalinux:python3.12-tkinter	3.12.5-2.el9_5.2 · AlmaLinux:9	Package registry (OSV)
alpine:python3	3.12.8-r1 · Alpine:v3.20	Package registry (OSV)
debian:python3.13	3.13.1-2 · Debian:13	Package registry (OSV)
opensuse:python-aiohttp	3.11.16-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
opensuse:python312	3.12.8-150600.3.12.1 · openSUSE:Leap 15.6	Package registry (OSV)
opensuse:python312-core	3.12.8-150600.3.12.1 · openSUSE:Leap 15.6	Package registry (OSV)
opensuse:python312-documentation	3.12.8-150600.3.12.1 · openSUSE:Leap 15.6	Package registry (OSV)
opensuse:python313	3.13.1-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
red hat:python-unversioned-command	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-debug	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-devel	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-idle	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-libs	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-test	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3-tkinter	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3.12	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3.12-debuginfo	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)
red hat:python3.12-debugsource	0:3.12.9-1.el10 · Red Hat:enterprise_linux:10.0	Package registry (OSV)

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.

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.

Seth Larsoncoordinator
J. Nick Kostonreporter

Not on record for this CVE: EPSS history · variant or chain candidate · public bounty program.

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.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/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

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:10 PM UTC

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

References

github.com/python/cpython/commit/71e8429ac8e2adc10084ab5ec29a62f4b6671a82

Show all references (7 more)

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

All records