What is CVE-2021-3348?

CVE-2021-3348 is a high-severity vulnerability in Linux Kernel, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.0/10. Published 2021-02-01.

How severe is CVE-2021-3348?

High severity. CVSS v3 base score is 7.0 out of 10.

Use After Free in Linux Kernel

CVE-2021-3348

nbd_add_socket in drivers/block/nbd.c in the Linux kernel through 5.10.12 has an ndb_queue_rq use-after-free that could be triggered by local attackers (with access to the nbd device) via an I/O request at a certain point during device setup, aka CID-b98e762e3d71.

Vulnerability class: Race Condition

Published 2021-02-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.003 (16.2th percentile), scored 2026-10-06.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Linux Kernel
Debian Linux — versions 9.0

Weakness classification (CWE)

References

git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/ (Patch, Mailing List, Vendor Advisory)
www.openwall.com/lists/oss-security/2021/01/28/3 (Patch, Mailing List, Third Party Advisory)
www.openwall.com/lists/oss-security/2021/02/01/1 (mailing-list, Patch, Mailing List, Third Party Advisory)
lists.debian.org/debian-lts-announce/2021/03/msg00035.html (mailing-list, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3348?: CVE-2021-3348 is a high-severity vulnerability in Linux Kernel, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.0/10. Published 2021-02-01.
How severe is CVE-2021-3348?: High severity. CVSS v3 base score is 7.0 out of 10.