What is CVE-2023-6660?

CVE-2023-6660 is a medium-severity vulnerability in FreeBSD. CVSS score: 6.5/10. Published 2023-12-13.

How severe is CVE-2023-6660?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Is CVE-2023-6660 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in FreeBSD

CVE-2023-6660

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.

Published 2023-12-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.006 (47.7th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

FreeBSD — versions 14.0, 14.0-RELEASE, 13.2

Public proof-of-concept exploits

References

security.freebsd.org/advisories/FreeBSD-SA-23:18.nfsclient.asc (vendor-advisory, Vendor Advisory)
security.netapp.com/advisory/ntap-20240322-0002/

Frequently asked questions

What is CVE-2023-6660?: CVE-2023-6660 is a medium-severity vulnerability in FreeBSD. CVSS score: 6.5/10. Published 2023-12-13.
How severe is CVE-2023-6660?: Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2023-6660 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.