CVE-2023-4091

Publication date 10 October 2023

Last updated 19 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
samba	25.10 questing	Fixed 2:4.18.6+dfsg-1ubuntu2.1
	25.04 plucky	Fixed 2:4.18.6+dfsg-1ubuntu2.1
	24.10 oracular	Fixed 2:4.18.6+dfsg-1ubuntu2.1
	24.04 LTS noble	Fixed 2:4.18.6+dfsg-1ubuntu2.1
	23.10 mantic	Fixed 2:4.18.6+dfsg-1ubuntu2.1
	23.04 lunar	Fixed 2:4.17.7+dfsg-1ubuntu2.3
	22.04 LTS jammy	Fixed 2:4.15.13+dfsg-0ubuntu1.5
	20.04 LTS focal	Fixed 2:4.15.13+dfsg-0ubuntu0.20.04.6
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation
	14.04 LTS trusty	Needs evaluation

Notes

mdeslaur

only vulnerable when using non-default configuraton: acl_xattr:ignore system acls = yes

Severity score breakdown

Parameter	Value
Base score	6.5 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	High
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N