CVE-2021-46974 bpf: Fix masking negation logic upon negative dst register

What is CVE-2021-46974?

CVE-2021-46974 is a high-severity vulnerability in Linux kernel, published on 27 Feb 2024. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix masking negation logic upon negative dst register

The negation logic for the case where the off_reg is sitting in the dst register is not correct given then we cannot just invert the add to a sub or vice versa. As a fix, perform the final bitwise and-op unconditionally into AX from the off_reg, then move the pointer from the src to dst and finally use AX as the source for the original pointer arithmetic operation such that the inversion yields a correct result. The single non-AX mov in between is possible given constant blinding is retaining it as it's not an immediate based operation.

Which versions are affected by CVE-2021-46974?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2021-46974?

Apply the vendor's patch.

Is CVE-2021-46974 being exploited?

There is no known exploitation of CVE-2021-46974 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-2021-46974, GHSA-78xq-q56p-fpwx, UBUNTU-CVE-2021-46974.