Security readout for executives and security teams
Plain-English summary
CVE-2021-3489 is a Linux kernel eBPF ring buffer flaw. A local low-privileged attacker could trigger kernel out-of-bounds writes and potentially execute code with kernel-level impact. It is serious, but the published scoring requires local access and high attack complexity.
Executive priority
Treat as high priority for shared Linux infrastructure and platforms running untrusted local code. This is not evidenced as internet-remote or actively exploited in the provided sources, but successful exploitation could compromise the kernel and the host.
Technical view
The issue is in bpf_ringbuf_reserve(), which failed to reject reserve requests larger than the ring buffer. It was introduced with BPF ring buffer support in v5.8-rc1 and fixed by commit 4b81ccebaeee, released in v5.13-rc4 and stable kernels v5.12.4, v5.11.21, and v5.10.37.
Likely exposure
Exposure is most likely on Linux systems running affected 5.8 through unfixed 5.10, 5.11, or 5.12 kernel lines, especially where low-privileged local users or untrusted workloads can access eBPF functionality.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. ZDI and oss-security describe code execution impact, but available evidence supports local, high-complexity exploitation requiring low privileges, not remote exploitation.
Researcher notes
Focus validation on kernel lineage, vendor backports, and eBPF exposure. The core fix denies reserve sizes larger than the ring buffer. Evidence is strong for root-cause and fixed versions, but incomplete for real-world exploitation prevalence.
Mitigation direction
- Upgrade to a vendor kernel containing the upstream fix.
- For stable kernels, ensure versions are at least 5.10.37, 5.11.21, or 5.12.4.
- Apply relevant Ubuntu or platform vendor security updates where applicable.
- Prioritize shared hosts, developer systems, and container platforms with untrusted local workloads.
- If patching is delayed, reduce local access to affected systems.
Validation and detection
- Inventory Linux kernel versions across servers, workstations, and container hosts.
- Compare installed kernels against affected and fixed versions in the advisories.
- Confirm vendor packages include commit 4b81ccebaeee or equivalent backport.
- Identify systems where low-privileged users or untrusted workloads can exercise eBPF.
- Track remediation through kernel package deployment and reboot completion.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-119: Exact CWE lookup
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Open ATT&CK lookupCWE-787: Exact CWE lookup
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Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-3489 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H1.16Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- [oss-security] CVE-2021-3489 - Linux kernel eBPF RINGBUF map oversized allocationCVE reference · mailing-list, x_refsource_MLIST
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=4b81ccebaeee885ab1aa1438133f2991e3a2b6eaCVE reference · x_refsource_MISC
- https://www.zerodayinitiative.com/advisories/ZDI-21-590/CVE reference · x_refsource_MISC
- https://ubuntu.com/security/notices/USN-4950-1CVE reference · vendor-advisory, x_refsource_UBUNTU
- https://ubuntu.com/security/notices/USN-4949-1CVE reference · vendor-advisory, x_refsource_UBUNTU
- https://security.netapp.com/advisory/ntap-20210716-0004/CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.