CVE-2021-4203 Use after free in kernel

What is CVE-2021-4203?

CVE-2021-4203 is a medium-severity use after free vulnerability in Linux kernel, published on 25 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

A use-after-free read flaw was found in sock_getsockopt() in net/core/sock.c due to SO_PEERCRED and SO_PEERGROUPS race with listen() (and connect()) in the Linux kernel. In this flaw, an attacker with a user privileges may crash the system or leak internal kernel information.

Weakness: CWE-416, CWE-362

Which versions are affected by CVE-2021-4203?

It affects 16 products.

Products include Linux kernel, Netapp A700s Firmware, Netapp Active Iq Unified Manager, Netapp Bootstrap Os, Netapp E-Series Santricity Os Controller, Netapp Element Software and 10 more.

How do I fix CVE-2021-4203?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-4203 being exploited?

There is no known exploitation of CVE-2021-4203 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-4203, GHSA-rh28-76xv-jcqc, UBUNTU-CVE-2021-4203.