CVE-2021-47036
A critical flaw in the Linux kernel’s handling of UDP tunnels could corrupt inner traffic. The bug allows the kernel to incorrectly aggregate packets, potentially causing data loss or delays. It has been fixed in a kernel patch.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Linux kernel, any distribution using a kernel version before the patch that enabled GRO for UDP tunnels. Typical users are system administrators and operators of Linux servers.
Real-world impact
An attacker could send crafted UDP packets that trigger the faulty aggregation, leading to corruption or loss of inner traffic such as VXLAN or other tunneled protocols. This could disrupt network services or degrade performance.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability is exploitable over the network, requires no user interaction, and can compromise confidentiality, integrity, and availability of all traffic passing through the affected kernel.
What to do about it
- 011. Update your Linux kernel to a version that includes the fix for CVE-2021-47036.
- 022. Verify the kernel version to ensure the patch is applied.
NVD-referenced vendor advisory
Timeline
- Feb 28, 2024 · Feb 28, 2024PublishedDisclosed and added to the National Vulnerability Database.
- Aug 4, 2026 · 2d agoAdvisory updatedThe NVD record was last revised.
- Aug 5, 2026 · 17h agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.