Cloudanix VulnDB

CVE-2025-21629

None

CVSS

—

EPSS

0.4%

Published

Jan 15, 2025

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A kernel networking setting was too restrictive for certain large IPv6 data transfers, which could slow things down and create warning messages until the operating system is updated.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Theoretical
Impact
Other
Component
OS kernel
Class
Misconfiguration
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

The kernel incorrectly disables NETIF_F_IPV6_CSUM hardware offload for IPv6 packets containing an IPV6_TLV_JUMBO extension header used by BIG TCP, forcing software checksum calculation and triggering skb_warn_bad_offload warnings during transmit path validation.

Why it matters to the business

Systems running affected kernels may experience reduced network throughput for large IPv6 flows, excessive kernel warning logs, and operational noise that complicates troubleshooting; high ecosystem prevalence in Linux distributions increases the scope of required updates across servers and appliances.

How an attack unfolds

An attacker does not directly exploit the flaw for code execution; instead the misconfiguration surfaces during normal high-volume IPv6 traffic on BIG TCP-enabled interfaces, causing repeated checksum fallback and log warnings that could be leveraged indirectly for denial-of-service via log flooding or performance degradation.

How to fix it

Upgrade to a fixed kernel version such as 6.1.124 or later commits containing ac9cfef69565021c9e1022a493a9c40b03e2caf9; rebuild and reboot affected systems; for packages such as simplesamlphp on Ubuntu 18.04 update to 1.14.15-1 or newer.

How to confirm the fix worked

Confirm the presence of the fix by checking kernel git commit ac9cfef69565021c9e1022a493a9c40b03e2caf9 or package version strings; reproduce BIG TCP IPv6 traffic and verify absence of skb_warn_bad_offload warnings in dmesg.

Typical attack path

  1. Enable BIG TCP and IPv6 on a device advertising NETIF_F_IPV6_CSUM
  2. Transmit large IPv6 packets that trigger the jumbo hopopt header for PF_PACKET observers
  3. Kernel path calls validate_xmit_skb and skb_csum_hwoffload_help
  4. skb_warn_bad_offload fires and checksum_help falls back to software

How to detect it

Search kernel logs for repeated skb_warn_bad_offload and skb_checksum_help call traces on systems with IPv6 BIG TCP traffic; review dmesg and journalctl for the specific warning signature around net/core/dev.c.

What your security team should do

  • Prioritize kernel upgrades on all externally facing and high-throughput systems within the next maintenance window
  • Monitor EPSS trend and kernel mailing lists for any follow-on issues
  • Temporarily disable BIG TCP on IPv6 interfaces if immediate patching is not feasible

The record

In the Linux kernel, the following vulnerability has been resolved: net: reenable NETIF_F_IPV6_CSUM offload for BIG TCP packets The blamed commit disabled hardware offoad of IPv6 packets with extension headers on devices that advertise NETIF_F_IPV6_CSUM, based on the definition of that feature in skbuff.h: * * - %NETIF_F_IPV6_CSUM * - Driver (device) is only able to checksum plain * TCP or UDP packets over IPv6. These are specifically * unencapsulated packets of the form IPv6|TCP or * IPv6|UDP where the Next Header field in the IPv6 * header is either TCP or UDP. IPv6 extension headers * are not supported with this feature. This feature * cannot be set in features for a device with * NETIF_F_HW_CSUM also set. This feature is being * DEPRECATED (see below). The change causes skb_warn_bad_offload to fire for BIG TCP packets. [ 496.310233] WARNING: CPU: 13 PID: 23472 at net/core/dev.c:3129 skb_warn_bad_offload+0xc4/0xe0 [ 496.310297] ? skb_warn_bad_offload+0xc4/0xe0 [ 496.310300] skb_checksum_help+0x129/0x1f0 [ 496.310303] skb_csum_hwoffload_help+0x150/0x1b0 [ 496.310306] validate_xmit_skb+0x159/0x270 [ 496.310309] validate_xmit_skb_list+0x41/0x70 [ 496.310312] sch_direct_xmit+0x5c/0x250 [ 496.310317] __qdisc_run+0x388/0x620 BIG TCP introduced an IPV6_TLV_JUMBO IPv6 extension header to communicate packet length, as this is an IPv6 jumbogram. But, the feature is only enabled on devices that support BIG TCP TSO. The header is only present for PF_PACKET taps like tcpdump, and not transmitted by physical devices. For this specific case of extension headers that are not transmitted, return to the situation before the blamed commit and support hardware offload. ipv6_has_hopopt_jumbo() tests not only whether this header is present, but also that it is the only extension header before a terminal (L4) header.

Affected packages

Ecosystem Package Introduced Fixed
Debian:11 linux 0 No fix
Debian:11 linux-6.1 0 6.1.128-1~deb11u1
Debian:11 linux-6.1 0 6.1.6.1.128-1~deb11u1
Debian:12 linux 0 No fix
Debian:13 linux 0 6.12.9-1
Linux Kernel 0 6.1.124
Mageia:9 dwarves 0 1.29-1.mga9
Mageia:9 kernel 0 6.6.74-1.mga9
Mageia:9 kernel-linus 0 6.6.74-1.mga9
Mageia:9 kmod-virtualbox 0 7.0.24-64.mga9
Mageia:9 kmod-xtables-addons 0 3.24-70.mga9
SUSE:Linux Enterprise High Availability Extension 15 SP6 kernel-default 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Live Patching 15 SP6 kernel-default 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Live Patching 15 SP6 kernel-livepatch-SLE15-SP6-RT_Update_11 0 1-150600.1.3.2
SUSE:Linux Enterprise Live Patching 15 SP6 kernel-livepatch-SLE15-SP6_Update_12 0 1-150600.13.3.1
SUSE:Linux Enterprise Module for Basesystem 15 SP6 kernel-64kb 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Basesystem 15 SP6 kernel-default 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Basesystem 15 SP6 kernel-default-base 0 6.4.0-150600.23.53.1.150600.12.24.1
SUSE:Linux Enterprise Module for Basesystem 15 SP6 kernel-source 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Basesystem 15 SP6 kernel-zfcpdump 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 kernel-coco 0 6.4.0-15061.28.coco15sp6.1
SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 kernel-coco_debug 0 6.4.0-15061.28.coco15sp6.1
SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 kernel-source-coco 0 6.4.0-15061.28.coco15sp6.1
SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 kernel-syms-coco 0 6.4.0-15061.28.coco15sp6.1
SUSE:Linux Enterprise Module for Development Tools 15 SP6 kernel-docs 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Development Tools 15 SP6 kernel-obs-build 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Development Tools 15 SP6 kernel-source 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Development Tools 15 SP6 kernel-syms 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Legacy 15 SP6 kernel-default 0 6.4.0-150600.23.53.1
SUSE:Linux Enterprise Module for Public Cloud 15 SP6 kernel-azure 0 6.4.0-150600.8.40.1
SUSE:Linux Enterprise Module for Public Cloud 15 SP6 kernel-source-azure 0 6.4.0-150600.8.40.1
SUSE:Linux Enterprise Module for Public Cloud 15 SP6 kernel-syms-azure 0 6.4.0-150600.8.40.1
SUSE:Linux Enterprise Workstation Extension 15 SP6 kernel-default 0 6.4.0-150600.23.53.1
SUSE:Real Time Module 15 SP6 kernel-rt 0 6.4.0-150600.10.39.1
SUSE:Real Time Module 15 SP6 kernel-rt_debug 0 6.4.0-150600.10.39.1
SUSE:Real Time Module 15 SP6 kernel-source-rt 0 6.4.0-150600.10.39.1
SUSE:Real Time Module 15 SP6 kernel-syms-rt 0 6.4.0-150600.10.39.1
Ubuntu:14.04:LTS linux 0 3.11.0-12.19
Ubuntu:14.04:LTS linux-aws 0 4.4.0-1002.2
Ubuntu:14.04:LTS linux-azure 0 4.15.0-1023.24~14.04.1
Ubuntu:14.04:LTS linux-lts-xenial 0 4.4.0-13.29~14.04.1
Ubuntu:16.04:LTS linux 0 4.4.0-2.16
Ubuntu:16.04:LTS linux-aws 0 4.4.0-1001.10
Ubuntu:16.04:LTS linux-aws-hwe 0 4.15.0-1030.31~16.04.1
Ubuntu:16.04:LTS linux-azure 0 4.11.0-1009.9
Ubuntu:16.04:LTS linux-gcp 0 4.10.0-1004.4
Ubuntu:16.04:LTS linux-hwe 0 4.8.0-39.42~16.04.1
Ubuntu:16.04:LTS linux-hwe-edge 0 No fix
Ubuntu:16.04:LTS linux-kvm 0 4.4.0-1004.9
Ubuntu:16.04:LTS linux-oracle 0 4.15.0-1007.9~16.04.1
Ubuntu:18.04:LTS linux 0 4.13.0-16.19
Ubuntu:18.04:LTS linux-aws 0 4.15.0-1001.1
Ubuntu:18.04:LTS linux-aws-5.0 0 No fix
Ubuntu:18.04:LTS linux-aws-5.3 0 No fix
Ubuntu:18.04:LTS linux-aws-5.4 0 5.4.0-1018.18~18.04.1
Ubuntu:18.04:LTS linux-azure 0 No fix
Ubuntu:18.04:LTS linux-azure-4.15 0 4.15.0-1082.92
Ubuntu:18.04:LTS linux-azure-5.3 0 No fix
Ubuntu:18.04:LTS linux-azure-5.4 0 5.4.0-1020.20~18.04.1
Ubuntu:18.04:LTS linux-azure-edge 0 No fix
Ubuntu:18.04:LTS linux-gcp 0 No fix
Ubuntu:18.04:LTS linux-gcp-4.15 0 4.15.0-1071.81
Ubuntu:18.04:LTS linux-gcp-5.3 0 No fix
Ubuntu:18.04:LTS linux-gcp-5.4 0 5.4.0-1019.19~18.04.2
Ubuntu:18.04:LTS linux-gke-4.15 0 No fix
Ubuntu:18.04:LTS linux-gke-5.4 0 No fix
Ubuntu:18.04:LTS linux-gkeop-5.4 0 No fix
Ubuntu:18.04:LTS linux-hwe 0 No fix
Ubuntu:18.04:LTS linux-hwe-5.4 0 5.4.0-37.41~18.04.1
Ubuntu:18.04:LTS linux-hwe-edge 0 No fix
Ubuntu:18.04:LTS linux-ibm-5.4 0 5.4.0-1010.11~18.04.2
Ubuntu:18.04:LTS linux-kvm 0 4.15.0-1002.2
Ubuntu:18.04:LTS linux-oem 0 No fix
Ubuntu:18.04:LTS linux-oracle 0 4.15.0-1007.9
Ubuntu:18.04:LTS linux-oracle-5.0 0 No fix
Ubuntu:18.04:LTS linux-oracle-5.3 0 No fix
Ubuntu:18.04:LTS linux-oracle-5.4 0 5.4.0-1019.19~18.04.1
Ubuntu:18.04:LTS linux-raspi-5.4 0 5.4.0-1013.13~18.04.1
Ubuntu:20.04:LTS linux 0 No fix
Ubuntu:20.04:LTS linux-aws 0 No fix
Ubuntu:20.04:LTS linux-aws-5.11 0 No fix
Ubuntu:20.04:LTS linux-aws-5.13 0 No fix
Ubuntu:20.04:LTS linux-aws-5.15 0 5.15.0-1014.18~20.04.1
Ubuntu:20.04:LTS linux-aws-5.8 0 No fix
Ubuntu:20.04:LTS linux-azure 0 5.4.0-1006.6
Ubuntu:20.04:LTS linux-azure-5.11 0 No fix
Ubuntu:20.04:LTS linux-azure-5.13 0 No fix
Ubuntu:20.04:LTS linux-azure-5.15 0 5.15.0-1007.8~20.04.1
Ubuntu:20.04:LTS linux-azure-5.8 0 No fix
Ubuntu:20.04:LTS linux-azure-fde 0 No fix
Ubuntu:20.04:LTS linux-azure-fde-5.15 0 No fix
Ubuntu:20.04:LTS linux-bluefield 0 5.4.0-1007.10
Ubuntu:20.04:LTS linux-gcp 0 5.4.0-1005.5
Ubuntu:20.04:LTS linux-gcp-5.11 0 No fix
Ubuntu:20.04:LTS linux-gcp-5.13 0 No fix
Ubuntu:20.04:LTS linux-gcp-5.15 0 5.15.0-1006.9~20.04.1
Ubuntu:20.04:LTS linux-gcp-5.8 0 No fix
Ubuntu:20.04:LTS linux-gke 0 No fix
Ubuntu:20.04:LTS linux-gke-5.15 0 No fix
Ubuntu:20.04:LTS linux-gkeop 0 No fix
Ubuntu:20.04:LTS linux-gkeop-5.15 0 No fix
Ubuntu:20.04:LTS linux-hwe-5.11 0 No fix
Ubuntu:20.04:LTS linux-hwe-5.13 0 No fix
Ubuntu:20.04:LTS linux-hwe-5.15 0 5.15.0-33.34~20.04.1
Ubuntu:20.04:LTS linux-hwe-5.8 0 No fix
Ubuntu:20.04:LTS linux-ibm 0 5.4.0-1003.4
Ubuntu:20.04:LTS linux-ibm-5.15 0 5.15.0-1033.36~20.04.1
Ubuntu:20.04:LTS linux-intel-5.13 0 No fix
Ubuntu:20.04:LTS linux-intel-iotg-5.15 0 5.15.0-1003.5~20.04.1
Ubuntu:20.04:LTS linux-iot 0 5.4.0-1001.3
Ubuntu:20.04:LTS linux-kvm 0 5.4.0-1004.4
Ubuntu:20.04:LTS linux-lowlatency-hwe-5.15 0 5.15.0-33.34~20.04.1
Ubuntu:20.04:LTS linux-oem-5.10 0 No fix
Ubuntu:20.04:LTS linux-oem-5.13 0 No fix
Ubuntu:20.04:LTS linux-oem-5.14 0 No fix
Ubuntu:20.04:LTS linux-oem-5.6 0 No fix
Ubuntu:20.04:LTS linux-oracle 0 5.4.0-1005.5
Ubuntu:20.04:LTS linux-oracle-5.11 0 No fix
Ubuntu:20.04:LTS linux-oracle-5.13 0 No fix
Ubuntu:20.04:LTS linux-oracle-5.15 0 5.15.0-1007.9~20.04.1
Ubuntu:20.04:LTS linux-oracle-5.8 0 No fix
Ubuntu:20.04:LTS linux-raspi 0 5.4.0-1007.7
Ubuntu:20.04:LTS linux-raspi2 0 No fix
Ubuntu:20.04:LTS linux-riscv 0 No fix
Ubuntu:20.04:LTS linux-riscv-5.11 0 No fix
Ubuntu:20.04:LTS linux-riscv-5.15 0 5.15.0-1015.17~20.04.1
Ubuntu:20.04:LTS linux-riscv-5.8 0 No fix
Ubuntu:20.04:LTS linux-xilinx-zynqmp 0 5.4.0-1020.24
Ubuntu:22.04:LTS linux 0 No fix
Ubuntu:22.04:LTS linux-allwinner-5.19 0 No fix
Ubuntu:22.04:LTS linux-aws 0 No fix
Ubuntu:22.04:LTS linux-aws-5.19 0 No fix
Ubuntu:22.04:LTS linux-aws-6.2 0 No fix
Ubuntu:22.04:LTS linux-aws-6.5 0 No fix
Ubuntu:22.04:LTS linux-aws-6.8 0 6.8.0-1009.9~22.04.2
Ubuntu:22.04:LTS linux-azure 0 No fix
Ubuntu:22.04:LTS linux-azure 0 5.13.0-1006.7
Ubuntu:22.04:LTS linux-azure-5.19 0 No fix
Ubuntu:22.04:LTS linux-azure-6.2 0 No fix
Ubuntu:22.04:LTS linux-azure-6.5 0 No fix
Ubuntu:22.04:LTS linux-azure-6.8 0 6.8.0-1008.8~22.04.1
Ubuntu:22.04:LTS linux-azure-fde 0 No fix
Ubuntu:22.04:LTS linux-azure-fde-5.19 0 No fix
Ubuntu:22.04:LTS linux-azure-fde-6.2 0 No fix
Ubuntu:22.04:LTS linux-gcp 0 No fix
Ubuntu:22.04:LTS linux-gcp 0 5.13.0-1005.6
Ubuntu:22.04:LTS linux-gcp-5.19 0 No fix
Ubuntu:22.04:LTS linux-gcp-6.2 0 No fix
Ubuntu:22.04:LTS linux-gcp-6.5 0 No fix
Ubuntu:22.04:LTS linux-gcp-6.8 0 6.8.0-1010.11~22.04.1
Ubuntu:22.04:LTS linux-gke 0 No fix
Ubuntu:22.04:LTS linux-gke 0 5.15.0-1002.2
Ubuntu:22.04:LTS linux-gkeop 0 No fix
Ubuntu:22.04:LTS linux-gkeop 0 5.15.0-1001.2
Ubuntu:22.04:LTS linux-hwe-5.19 0 No fix
Ubuntu:22.04:LTS linux-hwe-6.2 0 No fix
Ubuntu:22.04:LTS linux-hwe-6.5 0 No fix
Ubuntu:22.04:LTS linux-hwe-6.8 0 6.8.0-38.38~22.04.1
Ubuntu:22.04:LTS linux-ibm 0 No fix
Ubuntu:22.04:LTS linux-ibm 0 5.15.0-1002.2
Ubuntu:22.04:LTS linux-intel-iot-realtime 0 No fix
Ubuntu:22.04:LTS linux-intel-iot-realtime 0 5.15.0-1021.26
Ubuntu:22.04:LTS linux-intel-iotg 0 No fix
Ubuntu:22.04:LTS linux-intel-iotg 0 5.15.0-1004.6
Ubuntu:22.04:LTS linux-kvm 0 No fix
Ubuntu:22.04:LTS linux-kvm 0 5.13.0-1004.4
Ubuntu:22.04:LTS linux-lowlatency 0 No fix
Ubuntu:22.04:LTS linux-lowlatency 0 5.15.0-22.22
Ubuntu:22.04:LTS linux-lowlatency-hwe-5.19 0 No fix
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.2 0 No fix
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.5 0 No fix
Ubuntu:22.04:LTS linux-lowlatency-hwe-6.8 0 6.8.0-38.38.1~22.04.2
Ubuntu:22.04:LTS linux-nvidia 0 No fix
Ubuntu:22.04:LTS linux-nvidia 0 5.15.0-1005.5
Ubuntu:22.04:LTS linux-nvidia-6.2 0 No fix
Ubuntu:22.04:LTS linux-nvidia-6.5 0 No fix
Ubuntu:22.04:LTS linux-nvidia-6.8 0 6.8.0-1008.8~22.04.1
Ubuntu:22.04:LTS linux-nvidia-tegra 0 No fix
Ubuntu:22.04:LTS linux-nvidia-tegra-igx 0 No fix
Ubuntu:22.04:LTS linux-oem-5.17 0 No fix
Ubuntu:22.04:LTS linux-oem-6.0 0 No fix
Ubuntu:22.04:LTS linux-oem-6.1 0 No fix
Ubuntu:22.04:LTS linux-oem-6.5 0 No fix
Ubuntu:22.04:LTS linux-oracle 0 No fix
Ubuntu:22.04:LTS linux-oracle 0 5.13.0-1008.10
Ubuntu:22.04:LTS linux-oracle-6.5 0 No fix
Ubuntu:22.04:LTS linux-oracle-6.8 0 6.8.0-1006.6~22.04.3
Ubuntu:22.04:LTS linux-raspi 0 No fix
Ubuntu:22.04:LTS linux-raspi 0 5.13.0-1008.9
Ubuntu:22.04:LTS linux-realtime 0 No fix
Ubuntu:22.04:LTS linux-riscv 0 No fix
Ubuntu:22.04:LTS linux-riscv-5.19 0 No fix
Ubuntu:22.04:LTS linux-riscv-6.5 0 No fix
Ubuntu:22.04:LTS linux-riscv-6.8 0 6.8.0-38.38.1~22.04.1
Ubuntu:22.04:LTS linux-starfive-5.19 0 No fix
Ubuntu:22.04:LTS linux-starfive-6.2 0 No fix
Ubuntu:22.04:LTS linux-starfive-6.5 0 No fix
Ubuntu:22.04:LTS linux-xilinx-zynqmp 0 No fix
Ubuntu:22.04:LTS linux-xilinx-zynqmp 0 5.15.0-1022.26
Ubuntu:22.04:LTS:for:NVIDIA:BlueField linux-bluefield 0 No fix

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