CVE-2021-33624

Name: CVE-2021-33624
Creator: NVD / NIST
Published: 2021-06-23T16:15:07.957+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.7/10EPSS 0.92%

Last modified Jun 17, 2026

CVE-2021-33624 is a medium-severity vulnerability rated 4.7/10 on the CVSS scale. In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently an unprivileged BPF program can read arbitrary memory locations via a side-channel attack, aka CID-9183671af6db.. EPSS estimates a 0.92% chance of exploitation in the next 30 days.

Description

In kernel/bpf/verifier.c in the Linux kernel before 5.12.13, a branch can be mispredicted (e.g., because of type confusion) and consequently an unprivileged BPF program can read arbitrary memory locations via a side-channel attack, aka CID-9183671af6db.

Metrics

CVSS 3.1

4.7/10

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

EPSS Probability

0.92%

55.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-843

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	< 5.12.13
Debian	Debian Linux	9.0

References

http://www.openwall.com/lists/oss-security/2021/06/21/1Exploit, Mailing List, Third Party Advisory
https://github.com/benschlueter/CVE-2021-33624
https://github.com/torvalds/linux/commit/9183671af6dbf60a1219371d4ed73e23f43b49dbPatch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00010.htmlIssue Tracking, Third Party Advisory
https://www.usenix.org/conference/usenixsecurity21/presentation/kirznerThird Party Advisory
http://www.openwall.com/lists/oss-security/2021/06/21/1Exploit, Mailing List, Third Party Advisory
https://github.com/torvalds/linux/commit/9183671af6dbf60a1219371d4ed73e23f43b49dbPatch, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/10/msg00010.htmlIssue Tracking, Third Party Advisory
https://www.usenix.org/conference/usenixsecurity21/presentation/kirznerThird Party Advisory

Timeline

Published: Jun 23, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33624?

How severe is CVE-2021-33624?

CVE-2021-33624 has a CVSS score of 4.7/10 (MEDIUM severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33624?

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.

Are you affected by CVE-2021-33624?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST