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Fencer Vulns
high 8.6

CVE-2025-37799 json

vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp

published 2025-05-03 18 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-13363

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

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/payload data from prior processed packets).

We only noticed this through an MTU issue, e.g. when the XDP LB node and the backend node both had the same MTU (e.g. 1500) then the curl request got dropped on the backend node's NIC given the packet was too large even though the IPIP-encapped packet normally would never even come close to the MTU limit. Lowering the MTU on the XDP LB (e.g. 1480) allowed to let the curl request succeed (which also indicates that the kernel ignored the padding, and thus the issue wasn't very user-visible).

Commit e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") was too eager to also switch xdp_prepare_buff() from rcd->len to rbi->len. It really needs to stick to rcd->len which is the actual packet length from the descriptor. The latter we also feed into vmxnet3_process_xdp_small(), by the way, and it indicates the correct length needed to initialize the xdp->{data,data_end} parts. For e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") the relevant part was adapting xdp_init_buff() to address the warning given the xdp_data_hard_end() depends on xdp->frame_sz. With that fixed, traffic on the wire looks good again.

Patch / fix

  • Linux Linux 6.6.89, 6.8, 6.9, 6.12.26, 6.14.5, 6.15
  • linux Debian 14, Debian 13 6.12.27-1

debian advisories DEBIAN-CVE-2025-37799

  • linux Ubuntu 24.04 LTS 6.8.0-100.100
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1046.49
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1047.50
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1043.48
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1044.44
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1046.52
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1030.33
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1047.51

ubuntu advisories UBUNTU-CVE-2025-37799

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kpatch-patch-5_14_0-570_17_1 RHEL 9 1-3.el9_6
  • kernel RHEL 9 5.14.0-570.25.1.el9_6
  • rv RHEL 9 5.14.0-570.25.1.el9_6
  • perf RHEL 9 5.14.0-570.25.1.el9_6
  • rtla RHEL 9 5.14.0-570.25.1.el9_6
  • libperf RHEL 9 5.14.0-570.25.1.el9_6
  • kernel-rt RHEL 9 5.14.0-570.25.1.el9_6
  • kernel-64k RHEL 9 5.14.0-570.25.1.el9_6

red hat advisories RHSA-2025:10674RHSA-2025:10379RHSA-2025:10371

  • kernel-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-rt_debug Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-syms-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1

suse advisories SUSE-SU-2025:01972-1SUSE-SU-2025:01967-1SUSE-SU-2025:01964-1SUSE-SU-2025:01951-1SUSE-SU-2025:01919-1SUSE-SU-2025:01707-1

  • kernel-abi-stablelists AlmaLinux 10 6.12.0-55.20.1.el10_0
  • kernel AlmaLinux 9 5.14.0-570.25.1.el9_6
  • rv AlmaLinux 9 5.14.0-570.25.1.el9_6
  • perf AlmaLinux 9 5.14.0-570.25.1.el9_6
  • rtla AlmaLinux 9 5.14.0-570.25.1.el9_6
  • libperf AlmaLinux 9 5.14.0-570.25.1.el9_6
  • kernel-rt AlmaLinux 9 5.14.0-570.25.1.el9_6
  • kernel-64k AlmaLinux 9 5.14.0-570.25.1.el9_6

almalinux advisories ALSA-2025:10371ALSA-2025:10379

  • kernel Rocky Linux 9 5.14.0-570.25.1.el9_6
  • kernel Rocky Linux 10 6.12.0-55.20.1.el10_0

rocky linux advisories RLSA-2025:10379RLSA-2025:10371

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-37799 updated cvss 9.4

kernel: vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp

  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.25.1.el9_6, perf 5.14.0-570.25.1.el9_6, rtla 5.14.0-570.25.1.el9_6, python3-perf 5.14.0-570.25.1.el9_6, kernel-devel-matched 5.14.0-570.25.1.el9_6, kernel-64k-devel-matched 5.14.0-570.25.1.el9_6, +7 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10379
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.20.1.el10_0, perf 6.12.0-55.20.1.el10_0, rtla 6.12.0-55.20.1.el10_0, python3-perf 6.12.0-55.20.1.el10_0, kernel-devel-matched 6.12.0-55.20.1.el10_0, kernel-64k-devel-matched 6.12.0-55.20.1.el10_0, +7 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10371
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.25.1.el9_6, kernel-64k 5.14.0-570.25.1.el9_6, kernel-core 5.14.0-570.25.1.el9_6, kernel-tools 5.14.0-570.25.1.el9_6, kernel-modules 5.14.0-570.25.1.el9_6, kernel-64k-core 5.14.0-570.25.1.el9_6, +28 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10379
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.20.1.el10_0, kernel-64k 6.12.0-55.20.1.el10_0, kernel-core 6.12.0-55.20.1.el10_0, kernel-tools 6.12.0-55.20.1.el10_0, kernel-modules 6.12.0-55.20.1.el10_0, kernel-64k-core 6.12.0-55.20.1.el10_0, +27 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10371
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.25.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.25.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.25.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.25.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.25.1.el9_6
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10379
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.20.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.20.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.20.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.20.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.20.1.el10_0
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10371
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.25.1.el9_6, kernel-rt-64k 5.14.0-570.25.1.el9_6, kernel-rt-core 5.14.0-570.25.1.el9_6, kernel-rt-modules 5.14.0-570.25.1.el9_6, kernel-rt-64k-core 5.14.0-570.25.1.el9_6, kernel-rt-debug-core 5.14.0-570.25.1.el9_6, +14 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10379
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.20.1.el10_0, kernel-rt-64k 6.12.0-55.20.1.el10_0, kernel-rt-core 6.12.0-55.20.1.el10_0, kernel-rt-modules 6.12.0-55.20.1.el10_0, kernel-rt-64k-core 6.12.0-55.20.1.el10_0, kernel-rt-debug-core 6.12.0-55.20.1.el10_0, +14 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10371
show 3 more
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.25.1.el9_6, kernel-rt-kvm 5.14.0-570.25.1.el9_6, kernel-rt-core 5.14.0-570.25.1.el9_6, kernel-rt-modules 5.14.0-570.25.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.25.1.el9_6, kernel-rt-debug-core 5.14.0-570.25.1.el9_6, +6 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10379
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.20.1.el10_0, kernel-rt-kvm 6.12.0-55.20.1.el10_0, kernel-rt-core 6.12.0-55.20.1.el10_0, kernel-rt-modules 6.12.0-55.20.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.20.1.el10_0, kernel-rt-debug-core 6.12.0-55.20.1.el10_0, +6 more
    fixed: vendor fix “To mitigate this issue, prevent module vmxnet3 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.” RHSA-2025:10371
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.