Linux KernelOperating system · Linux
CVE-2021-34866
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThis vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.14-rc3. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs, which can result in a type confusion condition. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel. Was ZDI-CAN-14689.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA local privilege escalation vulnerability in Linux Kernel 5.14-rc3's eBPF program handling. The lack of proper validation of user-supplied eBPF programs leads to type confusion, allowing attackers who already have low-privileged code execution to escalate to kernel-level privileges and execute arbitrary code in kernel context.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 5.8, < 5.10.62>= 5.11, < 5.13.14all versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the Linux kernel versionRun 'uname -r' or 'cat /proc/version' to obtain the running kernel versionAffected if The kernel version falls within the affected ranges: >= 5.8 and < 5.10.62, or >= 5.11 and < 5.13.14
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Verify eBPF subsystem is availableCheck if the bpf() system call is functional by running 'ls /sys/kernel/debug/tracing' or attempting 'bpftool prog list' if availableAffected if The eBPF subsystem is loaded and functional on the system
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Determine if unprivileged eBPF is permittedCheck the kernel parameter 'kernel.unprivileged_bpf_disabled' using 'cat /proc/sys/kernel/unprivileged_bpf_disabled'Affected if The value is 0 (disabled), meaning unprivileged users can load eBPF programs, or if using a value of 1 with the sysctl wrapper showing no restrictions for the attack scenario
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Check for NetApp H-series firmware (if applicable)For NetApp H410c, H300s, H500s, H700s, H300e, H500e, or H700s, identify the firmware version through the BMC interface or 'ipmitool fru print'Affected if Any firmware version is present on the listed NetApp hardware platforms since all versions are affected
You are affected if your kernel version is within the vulnerable ranges AND the eBPF subsystem is enabled and accessible on your system, or if you are running any firmware version on the listed NetApp H-series hardware.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.10.625.13.14
Apply the Linux kernel security patch for CVE-2021-34866 when available; alternatively, disable eBPF if not required or enable kernel hardening features (like CONFIG_BPF_JIT_ALWAYS_ON) that restrict unprivileged eBPF program execution.
Linux Kernel 5.10.62 or later, or 5.13.14 or later
- Identify current kernel version using 'uname -r' or 'cat /proc/version'
- Check if version falls within affected range: >= 5.8 and < 5.10.62, OR >= 5.11 and < 5.13.14
- For production systems: schedule maintenance window and back up critical data
- Apply kernel upgrade via package manager (e.g., 'apt-get update && apt-get upgrade linux-image' or 'yum update kernel')
- Reboot system to load new kernel using 'systemctl reboot' or 'shutdown -r now'
- Verify new kernel version is >= 5.10.62 or >= 5.13.14 using 'uname -r'
- For NetApp H-series devices: contact vendor for firmware updates as listed in security.netapp.com advisory
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation6.0 h
- Implementation12.0 h
- Testing10.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34866 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-34866 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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