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

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Summary

CVECVE-2023-4091
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2023-11-03 08:15:08 UTC
Updated2026-11-07 14:16:56 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Problem Types: CWE-276 | CWE-276 Incorrect Default Permissions

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
3.1CNACVSS6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Samba Samba All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:4.18.6-2.el8_9 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:4.18.6-2.el8_9 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support unaffected 0:4.15.5-13.el8_6 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8.8 Extended Update Support unaffected 0:4.17.5-4.el8_8 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9 unaffected 0:4.18.6-101.el9_3 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9 unaffected 0:4.18.6-101.el9_3 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support unaffected 0:4.15.5-111.el9_0 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 9.2 Extended Update Support unaffected 0:4.17.5-104.el9_2 * rpm Not specified
CNA Red Hat Red Hat Virtualization 4 For Red Hat Enterprise Linux 8 unaffected 0:4.15.5-13.el8_6 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
CNA Red Hat Red Hat Storage 3 Not specified Not specified

References

ReferenceSourceLinkTags
Red Hat af854a3a-2127-422b-91ae-364da2661108 access.redhat.com Third Party Advisory
security.netapp.com/advisory/ntap-20231124-0002 af854a3a-2127-422b-91ae-364da2661108 security.netapp.com
Samba - Security Announcement Archive af854a3a-2127-422b-91ae-364da2661108 www.samba.org Vendor Advisory
access.redhat.com/errata/RHSA-2023:7467 af854a3a-2127-422b-91ae-364da2661108 access.redhat.com
access.redhat.com/errata/RHSA-2023:7408 af854a3a-2127-422b-91ae-364da2661108 access.redhat.com
[SECURITY] Fedora 39 Update: samba-4.19.2-1.fc39 - package-announce - Fedora Mailing-Lists af854a3a-2127-422b-91ae-364da2661108 lists.fedoraproject.org
access.redhat.com/errata/RHSA-2023:7464 af854a3a-2127-422b-91ae-364da2661108 access.redhat.com
Red Hat af854a3a-2127-422b-91ae-364da2661108 access.redhat.com Third Party Advisory
lists.debian.org/debian-lts-announce/2024/04/msg00015.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
access.redhat.com/errata/RHSA-2023:7371 af854a3a-2127-422b-91ae-364da2661108 access.redhat.com
cve-details af854a3a-2127-422b-91ae-364da2661108 access.redhat.com Third Party Advisory
15439 – (CVE-2023-4091) [SECURITY] CVE-2023-4091: Client can truncate file with read-only permissions af854a3a-2127-422b-91ae-364da2661108 bugzilla.samba.org Issue Tracking
2241882 – (CVE-2023-4091) CVE-2023-4091 samba: SMB clients can truncate files with read-only permissions af854a3a-2127-422b-91ae-364da2661108 bugzilla.redhat.com Issue Tracking
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
CNA2023-10-03T00:00:00.000ZReported to Red Hat.
CNA2023-10-10T00:00:00.000ZMade public.

Workarounds

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

Legacy QID Mappings

  • 161070 Oracle Enterprise Linux Security Update for samba (ELSA-2023-6744)
  • 161196 Oracle Enterprise Linux Security Update for samba (ELSA-2023-7467)
  • 199820 Ubuntu Security Notification for Samba Vulnerabilities (USN-6425-1)
  • 199907 Ubuntu Security Notification for Samba Vulnerabilities (USN-6425-3)
  • 242260 Red Hat Update for samba (RHSA-2023:6209)
  • 242318 Red Hat Update for samba (RHSA-2023:6744)
  • 242484 Red Hat Update for samba (RHSA-2023:7408)
  • 242507 Red Hat Update for samba (RHSA-2023:7467)
  • 242508 Red Hat Update for samba (RHSA-2023:7464)
  • 284612 Fedora Security Update for samba (FEDORA-2023-7eb8cbf1a5)
  • 284682 Fedora Security Update for samba (FEDORA-2023-fff0c857d6)
  • 285191 Fedora Security Update for samba (FEDORA-2023-8c9251e479)
  • 356630 Amazon Linux Security Advisory for samba : ALAS2023-2023-416
  • 356750 Amazon Linux Security Advisory for samba : ALAS2-2023-2367
  • 356781 Amazon Linux Security Advisory for samba : ALAS-2023-1896
  • 503395 Alpine Linux Security Update for samba
  • 505937 Alpine Linux Security Update for samba
  • 6000310 Debian Security Update for samba (DSA 5525-1)
  • 6000543 Debian Security Update for samba (DSA 5647-1)
  • 673360 EulerOS Security Update for samba (EulerOS-SA-2024-1097)
  • 673397 EulerOS Security Update for samba (EulerOS-SA-2023-3349)
  • 673574 EulerOS Security Update for samba (EulerOS-SA-2023-3286)
  • 673584 EulerOS Security Update for samba (EulerOS-SA-2024-1163)
  • 673680 EulerOS Security Update for samba (EulerOS-SA-2023-3258)
  • 673775 EulerOS Security Update for samba (EulerOS-SA-2024-1073)
  • 673833 EulerOS Security Update for samba (EulerOS-SA-2023-3317)
  • 673964 EulerOS Security Update for samba (EulerOS-SA-2024-1297)
  • 710873 Gentoo Linux Samba Multiple Vulnerabilities (GLSA 202402-28)
  • 755062 SUSE Enterprise Linux Security Update for samba (SUSE-SU-2023:4040-1)
  • 755069 SUSE Enterprise Linux Security Update for samba (SUSE-SU-2023:4046-1)
  • 755081 SUSE Enterprise Linux Security Update for samba (SUSE-SU-2023:4059-1)
  • 755106 SUSE Enterprise Linux Security Update for samba (SUSE-SU-2023:4096-1)
  • 941395 AlmaLinux Security Update for samba (ALSA-2023:6744)
  • 941422 AlmaLinux Security Update for samba (ALSA-2023:7467)

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