CVE-2026-23254
UDP GRO Checksum Validation Error in Linux Kernel Network Stack
Publication date: 2026-03-18
Last updated on: 2026-03-18
Assigner: kernel.org
Description
Description
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux_kernel | linux_kernel | * |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Linux kernel's network code related to Generic Receive Offload (GRO) for UDP packets. Specifically, the udp GRO complete stage incorrectly assumes that all packets received have the 'encapsulation' flag cleared. However, some hardware network interface cards (NICs) can set this flag when offloading checksum calculations for UDP encapsulated traffic. Additionally, certain drivers like the tun driver or setups using virtual Ethernet (veth) can create packets with this flag set.
Because of this incorrect assumption, the function udp4_gro_complete() uses the wrong network offset (inner instead of outer) to compute the UDP header checksum. This leads to checksum validation errors during packet processing.
The fix involves always clearing the encapsulation flag at the GRO completion stage and then setting it again as needed for encapsulated packets, ensuring correct checksum computation.
How can this vulnerability impact me? :
This vulnerability can cause incorrect checksum validation for UDP packets in certain network configurations involving hardware offloading or virtual network setups. As a result, packets might be incorrectly processed or dropped due to checksum errors.
Such errors can lead to network communication issues, degraded performance, or instability in systems relying on UDP traffic, especially in environments using hardware checksum offloading or virtual network interfaces.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
The vulnerability is resolved by fixing the handling of the encapsulation flag in the Linux kernel's UDP GRO completion stage. To mitigate this vulnerability, you should update your Linux kernel to a version that includes the fix for the udp GRO complete stage, which ensures the encapsulation flag is cleared properly at GRO completion time.