CVE-2021-4001

Description

A race condition was found in the Linux kernel's ebpf verifier between bpf_map_update_elem and bpf_map_freeze due to a missing lock in kernel/bpf/syscall.c. In this flaw, a local user with a special privilege (cap_sys_admin or cap_bpf) can modify the frozen mapped address space. This flaw affects kernel versions prior to 5.16 rc2.

CVSS Metrics

• v3.1•MEDIUM•Score: 4.1CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N
• v2.0•MEDIUM•Score: 4.7AV:L/AC:M/Au:N/C:N/I:C/A:N

EPSS Trends

Current EPSS score: 0.02%• Percentile: 4%

Techniques & Countermeasures

• CWE-367•Time-of-check Time-of-use (TOCTOU) Race Condition

  The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

Affected Systems

• linux•linux_kernel

  ≤ 5.15 | 5.16:rc1

References (2)

• https://bugzilla.redhat.com/show_bug.cgi?id=2025645
• https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=353050be4c19e102178ccc05988101887c25ae53