CVE-2023-4091

Samba: smb clients can truncate files with read-only permissions

publishedCWE-276

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.

Technical severity6.5 mediumCVSS 3.1 · CNA: redhat

Published2023-11-03Source updated 2026-11-07

Collected2026-11-072 attributed sources

Fixes and workarounds

Workaround

The vulnerability is most commonly associated with the "acl_xattr" module and can be mitigated by setting: ~~~ "acl_xattr:ignore system acls = no" ~~~

Source: CNA: redhat

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
Red Hat Enterprise Linux 8 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.18.6-2.el8_9; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.6 Extended Update Support Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.15.5-13.el8_6; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 8.8 Extended Update Support Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.17.5-4.el8_8; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.18.6-101.el9_3; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9.0 Extended Update Support Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.15.5-111.el9_0; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 9.2 Extended Update Support Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.17.5-104.el9_2; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Virtualization 4 for Red Hat Enterprise Linux 8 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	≥ 0:4.15.5-13.el8_6; < * (unaffected, rpm) Other versions: affected	CNA: redhat
Red Hat Enterprise Linux 6 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unknown	CNA: redhat
Red Hat Enterprise Linux 6 Red Hat `samba4` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unknown	CNA: redhat
Red Hat Enterprise Linux 7 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unknown	CNA: redhat
Red Hat Storage 3 Red Hat `samba` https://access.redhat.com/downloads/content/package-browser/	Range not reported Other versions: unknown	CNA: redhat

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
3.1 / 6.5 medium	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`	CNA: redhat

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://access.redhat.com/errata/RHSA-2023:6209CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2023:6744CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2023:7371CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2023:7408CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2023:7464CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2023:7467CNA: redhat · vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/security/cve/CVE-2023-4091CNA: redhat · vdb-entry, x_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2241882CNA: redhat · issue-tracking, x_refsource_REDHAT
https://bugzilla.samba.org/show_bug.cgi?id=15439CNA: redhat
https://www.samba.org/samba/security/CVE-2023-4091.htmlCNA: redhat
https://access.redhat.com/errata/RHSA-2023:6209ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/errata/RHSA-2023:6744ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/errata/RHSA-2023:7371ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/errata/RHSA-2023:7408ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/errata/RHSA-2023:7464ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/errata/RHSA-2023:7467ADP: CVE · vendor-advisory, x_refsource_REDHAT, x_transferred
https://access.redhat.com/security/cve/CVE-2023-4091ADP: CVE · vdb-entry, x_refsource_REDHAT, x_transferred
https://bugzilla.redhat.com/show_bug.cgi?id=2241882ADP: CVE · issue-tracking, x_refsource_REDHAT, x_transferred
https://bugzilla.samba.org/show_bug.cgi?id=15439ADP: CVE · x_transferred
https://lists.debian.org/debian-lts-announce/2024/04/msg00015.htmlADP: CVE · x_transferred
https://lists.fedoraproject.org/archives/list/[email protected]/message/ZUMVALLFFDFC53JZMUWA6HPD7HUGAP5I/ADP: CVE · x_transferred
https://security.netapp.com/advisory/ntap-20231124-0002/ADP: CVE · x_transferred
https://www.samba.org/samba/security/CVE-2023-4091.htmlADP: CVE · x_transferred

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