CVE-2021-3490

Published: 11 May 2021

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

From the Ubuntu Security Team

Manfred Paul discovered that the eBPF implementation in the Linux kernel did not properly track bounds on bitwise operations. A local attacker could use this to cause a denial of service (system crash) or execute arbitrary code.

Notes

introduced in v5.7-rc1

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3490
• https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=049c4e13714ecbca567b4d5f6d563f05d431c80e
• https://www.openwall.com/lists/oss-security/2021/05/11/11
• https://ubuntu.com/security/notices/USN-4948-1
• https://ubuntu.com/security/notices/USN-4949-1
• https://ubuntu.com/security/notices/USN-4950-1
• NVD
• Launchpad
• Debian