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CVE-2023-4091

MEDIUMCVSS 6.5/10EPSS 1.17%

Last modified

CVE-2023-4091 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 1.17% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
6.5/10

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

EPSS Probability
1.17%

63.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
SambaSamba< 4.17.12
SambaSamba>= 4.18.0, < 4.18.8
SambaSamba>= 4.19.0, < 4.19.1
FedoraprojectFedora39
RedhatStorage3.0
RedhatEnterprise Linux8.0
RedhatEnterprise Linux Eus9.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2023-4091?
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.
How severe is CVE-2023-4091?
CVE-2023-4091 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.17% probability of exploitation in the next 30 days.
How do I fix CVE-2023-4091?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST