Dulwich has an arbitrary file write via NTFS-hostile tree entries on Windows (CVE-2026-42305)
Published Last modified Sources: Red Hat, OSV, CVE.org, BSI
What is affected, what to do
A flaw was found in Dulwich, a pure-Python implementation of the Git file formats and protocols. A remote attacker could exploit this vulnerability by enticing a user on a Windows system to clone or check out a specially crafted malicious Git repository.
The available sources name no fixed version. Check the vendor guidance in the references below.
- Affected
- Jelmer Dulwich
gte 0.10.0, < 1.2.5..*
- Jelmer Dulwich
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Metrics
8.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
8.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: Red Hat, OSV, CVE.org, BSI
0.6 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 50.4
Show all metrics
- Severity
- High
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- 82.98 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- 8.8 Methodology
CVSS v3
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- 8.8
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- 0.6 %
- 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- 50.4
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
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
- CISA assessment (SSVC)
- Exploitation: none known · not automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 11 June 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-22
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- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
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 Dulwich, a pure-Python implementation of the Git file formats and protocols. A remote attacker could exploit this vulnerability by enticing a user on a Windows system to clone or check out a specially crafted malicious Git repository. This could lead to an arbitrary file write, ultimately resulting in remote code execution on the affected system.
Source: redhat_csaf, OSV (Open Source Vulnerabilities), cvelistv5, NVD (NIST), CVE.org (MITRE), BSI WID Portal, BSI CSAF
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| jelmer | dulwich |
|
|
| Oracle | Solaris |
|
|
| pypi | dulwich |
|
|
Vendors and products
Weakness classes (CWE)
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Base
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Entry at MITRE CWE-22
References & sources
- github.comjelmer/dulwich/security/advisories/GHSA-897w-fcg9-f6xjweb, x_refsource_CONFIRM
- NVD (NIST)vuln/detail/CVE-2026-42305advisory
- github.comjelmer/dulwich/commit/49eb56e51aad637fc23d54bf2a08cb42739b8290web, x_refsource_MISC
- github.comjelmer/dulwich/commit/57efc4aa1581e038915a0fd79365be53b150f4a9web, x_refsource_MISC
- github.comjelmer/dulwichpackage
- github.comjelmer/dulwich/releases/tag/dulwich-1.2.5web, x_refsource_MISC
- pypi.orgproject/dulwichpackage
- GitHub Security Advisoriesadvisories/GHSA-897w-fcg9-f6xjadvisory
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).
ReceivedGitHub
CVSS V3.1: AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness type: CWE-22
Description added or changed
New references:Show 7 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —Dulwich is a pure-Python implementation of the Git file formats and protocols. Versions starting with 0.10.0 and prior to 1.2.5 have an arbitrary file write leading to remote code execution when cloning or checking out a malicious Git repository on Windows. Dulwich's path-element validator accepted tree entries whose filenames contained bytes that Windows interprets as structural path syntax. Contributing configuration bugs made matters worse. The core.protectNTFS and core.protectHFS settings were looked up under a wrong option name and so user-set values were silently ignored, and core.protectNTFS only defaulted to true on Windows (Git upstream has defaulted it to true everywhere since CVE-2019-1353). Both have been corrected. Anyone who clones, fetches, or checks out an untrusted repository with Dulwich on Windows - either through the Dulwich CLI, porcelain.clone, or any downstream tool built on Dulwich - is impacted. POSIX clones are not directly exploitable (on POSIX \ is a literal filename byte), but a POSIX user can unknowingly propagate a malicious tree to Windows consumers via push or re-publication. This issue is fixed in Dulwich 1.2.5. Users should upgrade to 1.2.5 or later. There is no effective pre-patch workaround. On affected versions the core.protectNTFS configuration key was silently ignored, so setting it to true does not mitigate the issue. Users who cannot upgrade should avoid cloning, fetching, or checking out untrusted repositories with Dulwich on Windows. After upgrading the NTFS validator is on by default on every platform, so no additional configuration is required.CVSS added —AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HWeakness type (CWE) added —CWE-22Reference added —https://github.com/jelmer/dulwich/commit/49eb56e51aad637fc23d54bf2a08cb42739b8290Reference added —https://github.com/jelmer/dulwich/commit/57efc4aa1581e038915a0fd79365be53b150f4a9Reference added —https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5Reference added —https://github.com/jelmer/dulwich/security/advisories/GHSA-897w-fcg9-f6xjSource identifier: security-advisories@github.com
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-42305"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-42305.svg?lang=en" alt="CVE-2026-42305 – NEOSEC Intel" height="20"></a>