Medium [CVE-2021-4001] 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
This medium-severity Red Hat Linux advisory covers CVE-2021-4001 affecting Red Hat Enterprise Linux 8, Red Hat package: kernel-rt.
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Summary
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. The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.
This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space. A kernel update will be required to mitigate the flaw for the root or users with CAP_SYS_ADMIN capabilities.
Red Hat severity: Moderate — CVSS 6.7 (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-367.
Affected Red Hat products: Red Hat Enterprise Linux 8. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: kernel-rt.
- < 5.16
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
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