CVE-2021-33033

Name: CVE-2021-33033
Creator: NVD / NIST
Published: 2021-05-14T23:15:09.78+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 0.57%

Last modified Jun 17, 2026

CVE-2021-33033 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary value.. EPSS estimates a 0.57% chance of exploitation in the next 30 days.

Description

The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary value.

Metrics

CVSS 3.1

7.8/10

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

EPSS Probability

0.57%

42.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	< 5.11.14

References

https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14Mailing List, Patch, Vendor Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7Mailing List, Patch, Vendor Advisory
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8Mailing List, Patch, Vendor Advisory
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08Mailing List, Patch, Vendor Advisory
https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genoptExploit, Third Party Advisory
https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701eExploit, Mailing List, Third Party Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14Mailing List, Patch, Vendor Advisory
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7Mailing List, Patch, Vendor Advisory
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8Mailing List, Patch, Vendor Advisory
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08Mailing List, Patch, Vendor Advisory
https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genoptExploit, Third Party Advisory
https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701eExploit, Mailing List, Third Party Advisory

Timeline

Published: May 14, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33033?

How severe is CVE-2021-33033?

CVE-2021-33033 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.57% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33033?

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-2021-33033?

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

Scan your code now

Source: NVD / NIST