MediumCVE-2026-12345

Python Software Foundation CPython: Link Following (CVE-2026-12345)

Published 29.09.2026Last modified 26.10.2026Sources: Red Hat, BSI, CVE.org, OSV, Msrc Update Guide

Public exploit

What is affected, what to do

An exploit is publicly available. Update Python Software Foundation CPython to version 3.12.15, Python Software Foundation CPython to version 3.13.18, Python Software Foundation CPython to version 3.14.9.

Affected: Python Software Foundation CPython lt *..3.12.15
Python Software Foundation CPython lt 3.13.0..3.13.18
Python Software Foundation CPython lt 3.14.0..3.14.9
Python Software Foundation CPython lt 3.15.0a1..3.15.0rc3
Fixed in: Python Software Foundation CPython 3.12.15
Python Software Foundation CPython 3.13.18
Python Software Foundation CPython 3.14.9
Python Software Foundation CPython 3.15.0rc3

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

5.9

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v4

5.9

CVSS v4

Severity Medium on the scale from 0 to 10.

Source: Red Hat, BSI, CVE.org, OSV, Msrc Update Guide

0.3 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 27.9

Show all metrics

Severity: Medium
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 65.70 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 5.9 Methodology
CVSS v4 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 5.9
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.3 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 27.9; Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 29.09.2026
CISA assessment (SSVC): Exploitation: none known · not automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 29 September 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-59

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in Python. A race condition during the cleanup of temporary directories allows a local attacker with write access to replace a directory with a symbolic link (a reference pointing to another location). This can lead to unauthorized deletion or alteration of files outside the temporary directory, performed with the privileges of the process executing the cleanup.

Source: redhat_csaf, BSI WID Portal, BSI CSAF, cvelistv5, OSV (Open Source Vulnerabilities), NVD (NIST), Microsoft Security Update Guide

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Python Software Foundation	CPython	`3.15.0a1 – < 3.15.0rc3` `< 3.12.15` `3.13.0 – < 3.13.18` `3.14.0 – < 3.14.9`	`3.15.0rc3` `3.12.15` `3.13.18` `3.14.9`
Open Source	Python CPython	`< 3.15.0`	`3.15.0`

Distribution and container packages (9)

Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

Distribution and container packages
		Affected versions	Fixed in
bitnami	libpython	`3.13.0` `3.14.0` `—`	`3.13.18` `3.14.9` `3.12.16`
bitnami	python	`3.13.0` `3.14.0` `—`	`3.13.18` `3.14.9` `3.12.16`
bitnami	python-min	`3.14.0` `—` `3.13.0`	`3.14.9` `3.12.16` `3.13.18`

Vendors and products

Weakness classes (CWE)

CWE-59Improper Link Resolution Before File Access ('Link Following')
Base
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Entry at MITRE CWE-59

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

PoC-in-GitHub (nomi-sec)	CVE-2026-12345-poc (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	15.08.2026

References & sources

github.compython/cpython/pull/157580web, Patch
github.compython/cpython/issues/157579report, Issue tracking, web
github.compython/cpython/commit/5c20517a4fc56683efe63a7751020db9573f538dfix, Patch, web
openwall.comlists/oss-security/2026/09/29/40web
github.compython/cpython/commit/458e7134a5af7f86aee9d21b51cf499b41aa4420Patch, fix, web
github.compython/cpython/commit/e1f3590f155c6d66007e958c98c9d69316551993Patch, fix, web
github.compython/cpython/commit/06ef3d43fdaf4da97af12fa694b4886092c4b970fix, Patch, web
NVD (NIST)vuln/detail/CVE-2026-12345web
github.compython/cpython/commit/58ed0259cae509a19138795df302fe60b544dc74fix, Patch, web
github.compython/cpython/commit/0478b52788117db4b831b3efd648f56b777628aafix, Patch, web
github.compython/cpython/commit/c39b52d00b42200aaadff679e2fe3f1006d57c58fix, Patch, web

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

26.10.2026Record modifiedpython.org

New references:

Show 3 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12345.json">CVE-2026-12345</a>
Reference	added	—	https://github.com/python/cpython/commit/0478b52788117db4b831b3efd648f56b777628aa
Reference	added	—	https://github.com/python/cpython/commit/c39b52d00b42200aaadff679e2fe3f1006d57c58

Source identifier: cna@python.org

22.10.2026Record modifiedpython.org

1 individual change: Affected versions (publisher)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12345.json">CVE-2026-12345</a>

Source identifier: cna@python.org

10.10.2026Record modifiedpython.org
New references:
- https://github.com/python/cpython/commit/58ed0259cae509a19138795df302fe60b544dc74
Show the original change
Individual changes of this event as published by NVD
Type Action Before After
Reference added
—
https://github.com/python/cpython/commit/58ed0259cae509a19138795df302fe60b544dc74
Source identifier: cna@python.org

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/python/cpython/commit/58ed0259cae509a19138795df302fe60b544dc74

03.10.2026Record modifiedpython.org

New references:

https://github.com/python/cpython/commit/06ef3d43fdaf4da97af12fa694b4886092c4b970

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12345.json">CVE-2026-12345</a>
Reference	added	—	https://github.com/python/cpython/commit/06ef3d43fdaf4da97af12fa694b4886092c4b970

Source identifier: cna@python.org

30.09.2026Record modifiedpython.org

1 individual change: Affected versions (publisher)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	added	—	Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12345.json">CVE-2026-12345</a>

Source identifier: cna@python.org

Show 4 older changes

30.09.2026Record modifiedpython.org

New references:

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/python/cpython/commit/458e7134a5af7f86aee9d21b51cf499b41aa4420
Reference	added	—	https://github.com/python/cpython/commit/e1f3590f155c6d66007e958c98c9d69316551993

Source identifier: cna@python.org

29.09.2026Record modifiedCVE Program
New references:
- http://www.openwall.com/lists/oss-security/2026/09/29/40
Show the original change
Individual changes of this event as published by NVD
Type Action Before After
Reference added
—
http://www.openwall.com/lists/oss-security/2026/09/29/40
Source identifier: af854a3a-2127-422b-91ae-364da2661108

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	http://www.openwall.com/lists/oss-security/2026/09/29/40

29.09.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: none known, automatable: no

Weakness type: CWE-59

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Weakness type (CWE)	added	—	CWE-59
SSVC assessment	added	—	{"id":"CVE-2026-12345","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-29T18:38:00.590353Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

29.09.2026Receivedpython.org

CVSS V4.0: AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

Description added or changed

New references:

Show 6 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	The cleanup of tempfile.TemporaryDirectory is vulnerable to a race condition. An attacker who can modify the tree during cleanup can replace a directory with a symbolic link, causing files outside of the temporary directory to be deleted or have their permissions and file flags reset, with the privileges of the process performing the cleanup. Note that platforms where shutil.rmtree.avoids_symlink_attacks is false, remain affected, and file flags may still be reset outside of the tree on all platforms.
CVSS	added	—	AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/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
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12345.json">CVE-2026-12345</a>
Reference	added	—	https://github.com/python/cpython/commit/5c20517a4fc56683efe63a7751020db9573f538d
Reference	added	—	https://github.com/python/cpython/issues/157579
Reference	added	—	https://github.com/python/cpython/pull/157580

Source identifier: cna@python.org

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