medium
6.5
CWE
276
Advisory Published
CVE Published
CVE Published
Updated

CVE-2023-4091: Samba: smb clients can truncate files with read-only permissions

First published: Tue Oct 03 2023(Updated: )

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.

Credit: secalert@redhat.com secalert@redhat.com

Affected SoftwareAffected VersionHow to fix
redhat/samba<4.19.1
4.19.1
redhat/samba<4.18.8
4.18.8
redhat/samba<4.17.12
4.17.12
Samba Samba<4.17.12
Samba Samba>=4.18.0<4.18.8
Samba Samba>=4.19.0<4.19.1
Fedoraproject Fedora=39
Redhat Storage=3.0
Redhat Enterprise Linux=8.0
Redhat Enterprise Linux Eus=9.0
ubuntu/samba<2:4.15.13+dfsg-0ubuntu0.20.04.6
2:4.15.13+dfsg-0ubuntu0.20.04.6
ubuntu/samba<2:4.15.13+dfsg-0ubuntu1.5
2:4.15.13+dfsg-0ubuntu1.5
ubuntu/samba<2:4.17.7+dfsg-1ubuntu2.3
2:4.17.7+dfsg-1ubuntu2.3
ubuntu/samba<2:4.18.6+dfsg-1ubuntu2.1
2:4.18.6+dfsg-1ubuntu2.1
ubuntu/samba<2:4.18.6+dfsg-1ubuntu2.1
2:4.18.6+dfsg-1ubuntu2.1
debian/samba
2:4.13.13+dfsg-1~deb11u6
2:4.17.12+dfsg-0+deb12u1
2:4.21.0~rc1+really4.20.3+dfsg-1
2:4.21.0~rc1+really4.20.4+dfsg-1

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is CVE-2023-4091?

    CVE-2023-4091 is a vulnerability that allows SMB clients to truncate files with read-only permissions.

  • How does CVE-2023-4091 impact SMB clients?

    CVE-2023-4091 allows SMB clients to truncate files even if they only have read-only permissions.

  • Which software is affected by CVE-2023-4091?

    Samba versions up to 2:4.15.13+dfsg-0ubuntu0.20.04.6, 2:4.15.13+dfsg-0ubuntu1.5, and 2:4.17.7+dfsg-1ubuntu2.3 are affected by CVE-2023-4091.

  • How can I fix CVE-2023-4091?

    To fix CVE-2023-4091, update Samba to version 2:4.15.13+dfsg-0ubuntu0.20.04.6, 2:4.15.13+dfsg-0ubuntu1.5, or 2:4.17.7+dfsg-1ubuntu2.3 depending on your Ubuntu release.

  • Where can I find more information about CVE-2023-4091?

    You can find more information about CVE-2023-4091 on the MITRE CVE website (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4091), the Samba security page (https://www.samba.org/samba/security/CVE-2023-4091.html), and the Ubuntu security notices (https://ubuntu.com/security/notices/USN-6425-1).

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