FreeBSD : FreeBSD -- NFS client data corruption and kernel memory disclosure (8eefff69-997f-11ee-8e38-002590c1f29c)

medium Nessus Plugin ID 186807



The remote FreeBSD host is missing one or more security-related updates.


The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the 8eefff69-997f-11ee-8e38-002590c1f29c advisory.

- In FreeBSD 13.2 and 14.0, the NFS client was optimized to improve the performance of IO_APPEND writes, that is, writes which add data to the end of a file and so extend its size. This uncovered an old bug in some routines which copy userspace data into the kernel. The bug also affects the NFS client's implementation of direct I/O; however, this implementation is disabled by default by the vfs.nfs.nfs_directio_enable sysctl and is only used to handle synchronous writes. When a program running on an affected system appends data to a file via an NFS client mount, the bug can cause the NFS client to fail to copy in the data to be written but proceed as though the copy operation had succeeded. This means that the data to be written is instead replaced with whatever data had been in the packet buffer previously. Thus, an unprivileged user with access to an affected system may abuse the bug to trigger disclosure of sensitive information. In particular, the leak is limited to data previously stored in mbufs, which are used for network transmission and reception, and for certain types of inter- process communication. The bug can also be triggered unintentionally by system applications, in which case the data written by the application to an NFS mount may be corrupted. Corrupted data is written over the network to the NFS server, and thus also susceptible to being snooped by other hosts on the network. Note that the bug exists only in the NFS client; the version and implementation of the server has no effect on whether a given system is affected by the problem.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.


Update the affected packages.

See Also

Plugin Details

Severity: Medium

ID: 186807

File Name: freebsd_pkg_8eefff69997f11ee8e38002590c1f29c.nasl

Version: 1.1

Type: local

Published: 12/13/2023

Updated: 12/21/2023

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information


Risk Factor: Low

Score: 3.6


Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:N/A:N

CVSS Score Source: CVE-2023-6660


Risk Factor: Medium

Base Score: 6.5

Temporal Score: 5.7

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:freebsd-kernel, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Settings/ParanoidReport, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Exploit Ease: No known exploits are available

Patch Publication Date: 12/13/2023

Vulnerability Publication Date: 12/13/2023

Reference Information

CVE: CVE-2023-6660