CVE-2025-37799

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp

vmxnet3 driver's XDP handling is buggy for packet sizes using ring0 (that

is, packet sizes between 128 - 3k bytes).

We noticed MTU-related connectivity issues with Cilium's service load-

balancing in case of vmxnet3 as NIC underneath. A simple curl to a HTTP

backend service where the XDP LB was doing IPIP encap led to overly large

packet sizes but only for *some* of the packets (e.g. HTTP GET request)

while others (e.g. the prior TCP 3WHS) looked completely fine on the wire.

In fact, the pcap recording on the backend node actually revealed that the

node with the XDP LB was leaking uninitialized kernel data onto the wire

for the affected packets, for example, while the packets should have been

152 bytes their actual size was 1482 bytes, so the remainder after 152 bytes

was padded with whatever other data was in that page at the time (e.g. we

saw user/payloa

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References