CVE-2021-4001: linux linux_kernel
Vulnerability summary
CVE-2021-4001 is a medium (CVSS 4.7) vulnerability in linux linux_kernel. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.2% of scored vulnerabilities.
Not severe (CVSS 4.1, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 15 · Related 13Timeline
- 21-01-2022PublishedVulnerability first disclosed.
- 08-10-2026Last modifiedVulnerability information updated.
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
4 scores · 3 sources · 2 versions- OSV · DebianEcosystem advisory · calculated4.1MediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N
- NVDNIST4.1MediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N
EPSS trend
Probability
0.19%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.19% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, administrative account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu65 products
- linux< 5.4.0-164.181
- linux-aws< 5.4.0-1111.120
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11< 5.11.0-1028.31~20.04.1
- linux-aws-5.13< 5.13.0-1012.13~20.04.1
Debian1 product
- linux< 5.15.5-1
Linux1 product
- linux_kernel≤ 5.15 | 5.16:rc1
3 vendors · 67 products
