Skip to content
Fencer Vulns
critical 9.8

CVE-2026-74269 in the critical feed json

bnxt: fix head underflow on XDP head-grow

published 2026-08-15 2 mo ago modified 2026-10-30 10 d ago also EUVD-2026-59416

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

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

bnxt: fix head underflow on XDP head-grow

The xdp.py test test_xdp_native_adjst_head_grow_data crashes when run on a bnxt machine (and also crashes in NIPA).

It seems that the bug is an underflow in bnxt_rx_multi_page_skb, which builds the skb head:

napi_build_skb(data_ptr - bp->rx_offset, rxr->rx_page_size);

The problem with this expression is that in page mode, rx_offset is:

bp->rx_offset = NET_IP_ALIGN + XDP_PACKET_HEADROOM;

Which evaluates (at least on x86_64) to 258.

The test test_xdp_native_adjst_head_grow_data tests a case where the head is adjusted by -256.

When this test runs, data_ptr is shifted to frag_start + 2 (where frag_start = page_address(page) + offset).

Then, bnxt_rx_multi_page_skb is invoked and the napi_build_skb expression subtracts 258, landing at an address before frag_start. This could be either the previous fragment or the previous physical page when the offset is < 256 (e.g. if the fragment started at offset 0).

When the skb is freed, the page pool fragment reference is dropped on either the wrong page or the wrong frag of the right page. In either case, the corrupted reference count can lead to the page being prematurely recycled while still in use. Once (incorrectly) recycled, it can be handed out again and on driver teardown this would result in a double free.

The commit under fixes updated this code to handle the case where the native page size is >= 64k, but it unintentionally broke the head grow case.

To fix this, add an offset field to struct bnxt_sw_rx_bd, mirroring the existing offset field in struct bnxt_sw_rx_agg_bd. Populate it on allocation and preserve it on reuse.

In bnxt_rx_multi_page_skb, use the newly added offset field to compute the fragment start and pass that to napi_build_skb. Adjust the layout with skb_reserve.

There are two cases, the non-adjustment case and the adjustment case.

In both cases, the skb is built at page_address(page) + offset to account for the case where the native page size >= 64K and skb_reserve is called with data_ptr - (page_address(page) + offset). That difference equals bp->rx_offset when data_ptr was not moved, or bp->rx_offset + xdp_adjust when XDP adjusted the head.

Re-running the failing test with this commit applied causes the test to run successfully to completion.

The other rx_skb_func implementations don't have this issue.

Patch / fix

  • Linux Linux 6.1.191, 6.5, 6.6.160, 6.12.114, 6.18.53, 7.1.5, 7.2
  • linux Debian 13 6.12.115-2
  • linux Debian 14 7.1.5-1

debian advisories DEBIAN-CVE-2026-74269

  • linux Ubuntu 26.04 LTS 7.0.0-34.34
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1013.13
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1013.13
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1007.8
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1014.14
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1020.20
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-34.34.1

ubuntu advisories UBUNTU-CVE-2026-74269

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

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:4120-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel Azure Linux 3.0 6.6.161.1-1

azure linux advisories AZL-96006

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-74269 updated cvss 7.0

kernel: bnxt: fix head underflow on XDP head-grow

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available
  • 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-selftests-internal
    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

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.