dulwich — security advisory
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
- Products
- dulwich
- Affected versions
- 0.11.2-1ubuntu1, 0.12.0-1, 0.12.0-1build1, 0.12.0-1build2, 0.18.2-1build1, 0.18.5-1, 0.19.11-2, 0.19.14-4ubuntu1, 0.19.15-1, 0.19.15-1build1, 0.20.15-1ubuntu1, 0.20.31-1.1, 0.20.31-1.1build1, 0.20.31-1ubuntu1, 0.21.6-1, 0.21.6-1build1, 0.21.6-1build2, 0.22.7-1, 0.24.2-2, 1.1.0-2ubuntu1, 1.1.0-3, 1.2.12-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-42305
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:03 UTC · Revision 1
Source evidence
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
osv:UBUNTU-CVE-2026-42305
dulwich
Fixed versions: Not specified
dulwich
Fixed versions: Not specified
dulwich
Fixed versions: Not specified
dulwich
Fixed versions: Not specified
dulwich
Fixed versions: Not specified
dulwich
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dulwich
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dulwich
Fixed versions: Not specified
Complete source record
{
"id": "0a0de5ed3525e258ccf82277851ee750b564249297ad41da387f7525a4a5054e",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-42305",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-42305",
"summary": "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",
"evidence": "osv:UBUNTU-CVE-2026-42305",
"products": [
{
"name": {
"value": "dulwich",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "0.11.2-1ubuntu1",
"evidence": "/affected/0/versions"
},
{
"value": "0.12.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.12.0-1build1",
"evidence": "/affected/0/versions"
},
{
"value": "0.12.0-1build2",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
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},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
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"evidence": "/affected/1/versions"
},
{
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"evidence": "/affected/1/versions"
}
]
},
{
"name": {
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"evidence": "/affected/2/package/name"
},
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"affected_versions": [
{
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"evidence": "/affected/2/versions"
},
{
"value": "0.19.14-4ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "0.19.15-1",
"evidence": "/affected/2/versions"
},
{
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"evidence": "/affected/2/versions"
}
]
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{
"name": {
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},
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"affected_versions": [
{
"value": "0.20.15-1ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "0.20.31-1ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "0.20.31-1.1",
"evidence": "/affected/3/versions"
},
{
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"evidence": "/affected/3/versions"
}
]
},
{
"name": {
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"affected_versions": [
{
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"evidence": "/affected/4/versions"
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{
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"evidence": "/affected/4/versions"
},
{
"value": "0.21.6-1build2",
"evidence": "/affected/4/versions"
}
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},
{
"name": {
"value": "dulwich",
"evidence": "/affected/5/package/name"
},
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"affected_versions": [
{
"value": "0.22.7-1",
"evidence": "/affected/5/versions"
}
]
},
{
"name": {
"value": "dulwich",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.1.0-3",
"evidence": "/affected/6/versions"
},
{
"value": "1.2.12-1",
"evidence": "/affected/6/versions"
}
]
},
{
"name": {
"value": "dulwich",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.22.7-1",
"evidence": "/affected/7/versions"
},
{
"value": "0.24.2-2",
"evidence": "/affected/7/versions"
},
{
"value": "1.1.0-2ubuntu1",
"evidence": "/affected/7/versions"
},
{
"value": "1.1.0-3",
"evidence": "/affected/7/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-42305",
"aliases": [
"UBUNTU-CVE-2026-42305"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "dulwich",
"purl": "pkg:deb/ubuntu/dulwich?arch=source&distro=xenial",
"ecosystem": "Ubuntu:16.04:LTS"
},
"versions": [
"0.11.2-1ubuntu1",
"0.12.0-1",
"0.12.0-1build1",
"0.12.0-1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42305.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "pypy-dulwich",
"binary_version": "0.12.0-1build2"
},
{
"binary_name": "python-dulwich",
"binary_version": "0.12.0-1build2"
},
{
"binary_name": "python3-dulwich",
"binary_version": "0.12.0-1build2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
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}
]
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],
"package": {
"name": "dulwich",
"purl": "pkg:deb/ubuntu/dulwich?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"0.18.2-1build1",
"0.18.5-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42305.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "pypy-dulwich",
"binary_version": "0.18.5-1"
},
{
"binary_name": "python-dulwich",
"binary_version": "0.18.5-1"
},
{
"binary_name": "python3-dulwich",
"binary_version": "0.18.5-1"
}
]
}
},
{
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],
"package": {
"name": "dulwich",
"purl": "pkg:deb/ubuntu/dulwich?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"0.19.11-2",
"0.19.14-4ubuntu1",
"0.19.15-1",
"0.19.15-1build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42305.json"
},
"ecosystem_specific": {
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{
"binary_name": "pypy-dulwich",
"binary_version": "0.19.15-1build1"
},
{
"binary_name": "python3-dulwich",
"binary_version": "0.19.15-1build1"
}
]
}
},
{
"ranges": [
{
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{
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}
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],
"package": {
"name": "dulwich",
"purl": "pkg:deb/ubuntu/dulwich?arch=source&distro=jammy",
"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
"0.20.15-1ubuntu1",
"0.20.31-1ubuntu1",
"0.20.31-1.1",
"0.20.31-1.1build1"
],
"database_specific": {
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},
"ecosystem_specific": {
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"ecosystem": "Ubuntu:24.04:LTS"
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"0.21.6-1build1",
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"ecosystem": "Ubuntu:26.10"
},
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"name": "dulwich",
"purl": "pkg:deb/ubuntu/dulwich?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
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"0.24.2-2",
"1.1.0-2ubuntu1",
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},
"ecosystem_specific": {
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{
"binary_name": "python3-dulwich",
"binary_version": "1.1.0-3"
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]
}
}
],
"modified": "2026-10-17T13:00:05.320874980Z",
"provider": "osv",
"upstream": [
"CVE-2026-42305"
],
"references": [
"https://ubuntu.com/security/CVE-2026-42305",
"https://www.cve.org/CVERecord?id=CVE-2026-42305",
"https://github.com/jelmer/dulwich/security/advisories/GHSA-897w-fcg9-f6xj"
]
},
"related_cves": [
{
"value": "CVE-2026-42305",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 360297,
"published_at": "2026-06-10T23:16:00+00:00"
}