Medium
Samba: smb clients can truncate files with read-only permissions
Type: advisorySources: OSV
A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "acl_xattr" is configured with "acl_xattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2023-4091
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 8 Nov 2026, 02:27 UTC · Revision 1
Source evidence
Samba: smb clients can truncate files with read-only permissions
core-osv · Original sourcePublished 3 Nov 2023, 07:56 UTC
A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module "acl_xattr" is configured with "acl_xattr:ignore system acls = yes". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.
osv:CVE-2023-4091
Complete source record
{
"id": "84fbcc25ebb0ffddb49b410fc2cd0fc0e872224f63c030ba9e19c0b3c26ff412",
"url": "https://osv.dev/vulnerability/CVE-2023-4091",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Samba: smb clients can truncate files with read-only permissions",
"summary": "A vulnerability was discovered in Samba, where the flaw allows SMB clients to truncate files, even with read-only permissions when the Samba VFS module \"acl_xattr\" is configured with \"acl_xattr:ignore system acls = yes\". The SMB protocol allows opening files when the client requests read-only access but then implicitly truncates the opened file to 0 bytes if the client specifies a separate OVERWRITE create disposition request. The issue arises in configurations that bypass kernel file system permissions checks, relying solely on Samba's permissions.",
"evidence": "osv:CVE-2023-4091",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2023-4091",
"aliases": [
"CVE-2023-4091"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N"
}
],
"affected": [
{
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{
"repo": "https://github.com/samba-team/samba",
"type": "GIT",
"events": [
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{
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"range": [
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{
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"source": "CPE_RANGE"
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{
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-4091.json"
}
}
],
"modified": "2026-10-28T02:30:52.751870821Z",
"provider": "osv",
"references": [
"https://access.redhat.com/downloads/content/package-browser/",
"https://lists.debian.org/debian-lts-announce/2024/04/msg00015.html",
"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZUMVALLFFDFC53JZMUWA6HPD7HUGAP5I/",
"https://www.samba.org/samba/security/CVE-2023-4091.html",
"https://access.redhat.com/errata/RHSA-2023:6209",
"https://access.redhat.com/errata/RHSA-2023:6744",
"https://access.redhat.com/errata/RHSA-2023:7371",
"https://access.redhat.com/errata/RHSA-2023:7408",
"https://access.redhat.com/errata/RHSA-2023:7464",
"https://access.redhat.com/errata/RHSA-2023:7467",
"https://access.redhat.com/security/cve/CVE-2023-4091",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/4xxx/CVE-2023-4091.json",
"https://nvd.nist.gov/vuln/detail/CVE-2023-4091",
"https://security.netapp.com/advisory/ntap-20231124-0002/",
"https://bugzilla.redhat.com/show_bug.cgi?id=2241882",
"https://bugzilla.samba.org/show_bug.cgi?id=15439"
],
"provider_metadata": {
"cwe_ids": [
"CWE-276"
],
"cna_assigner": "redhat",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"fixed": "0:4.18.6-2.el8_9"
},
{
"fixed": "0:4.18.6-2.el8_9"
},
{
"fixed": "0:4.15.5-13.el8_6"
},
{
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{
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{
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},
{
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}
],
"source": "AFFECTED_FIELD",
"strategy": "InverseAffectedRanges"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/4xxx/CVE-2023-4091.json"
}
},
"related_cves": [
{
"value": "CVE-2023-4091",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 521780,
"published_at": "2023-11-03T07:56:35.611+00:00"
}