CVE-2026-64525: xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit

Published Jul 25, 2026
·
Updated

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

xfrm: move policybydst RCU sync from per-netns .exit to .preexit

The struct pernetoperations docstring in include/net/netnamespace.h explicitly warns against blocking RCU primitives in .exit handlers:

Exit methods using blocking RCU primitives, such as synchronizercu(), should be implemented via exitbatch. [...] Please, avoid synchronizercu() at all, where it's possible.

Note that a combination of preexit() and exit() can be used, since a synchronizercu() is guaranteed between the calls.

xfrmpolicyfini() violates this: it calls synchronizercu() before freeing the policybydst hash tables (so no RCU reader is mid- traversal at free time), but runs from xfrmnetops.exit -- once per namespace -- so a cleanupnet() of N namespaces pays N full RCU grace periods serially.

Use the documented preexit/exit split. Move the policy flush (and the workqueue drains it depends on) into a new .preexit handler; xfrmpolicyfini() then runs in .exit and frees the hash tables after the synchronizercuexpedited() that cleanupnet() guarantees between the two phases. Providing O(1) RCU grace periods per batch instead of O(N).

Observed on Linux 6.18 with a workload doing unshare(CLONENEWNET) at ~13/sec sustained: cleanupnet() and the netnswq rescuer kthread both stuck in xfrmpolicyfini()'s synchronizercu(), >300k struct net accumulated in the cleanup queue, Percpu in /proc/meminfo climbed to 130+ GB on 256-CPU hosts, and memcg OOMs followed. setupnet and putnet counts were balanced, ruling out a refcount leak.

Affected Software

162 affected componentsFixes available
Linux Linux kernel
Microsoft azl3 kernel 6.6.157.1-1<6.6.159.1-1
6.6.159.1-1
ubuntu/linux-hwe-edge*
ubuntu/linux-aws-5.0*
ubuntu/linux-aws-5.3*
ubuntu/linux-azure*
ubuntu/linux-azure-5.3*
ubuntu/linux-azure-edge*
ubuntu/linux-gcp*
ubuntu/linux-gcp-5.3*
ubuntu/linux-gke-4.15*
ubuntu/linux-gke-5.4*
ubuntu/linux-gkeop-5.4*
ubuntu/linux-hwe*
ubuntu/linux-hwe-edge*
ubuntu/linux-oem*
ubuntu/linux-oracle-5.0*
ubuntu/linux-oracle-5.3*
ubuntu/linux-aws-5.11*
ubuntu/linux-aws-5.13*
ubuntu/linux-aws-5.8*
ubuntu/linux-azure-5.11*
ubuntu/linux-azure-5.13*
ubuntu/linux-azure-5.8*
ubuntu/linux-azure-fde*
ubuntu/linux-gcp-5.11*
ubuntu/linux-gcp-5.13*
ubuntu/linux-gcp-5.8*
ubuntu/linux-gke*
ubuntu/linux-gke-5.15*
ubuntu/linux-gkeop*
ubuntu/linux-gkeop-5.15*
ubuntu/linux-hwe-5.11*
ubuntu/linux-hwe-5.13*
ubuntu/linux-hwe-5.8*
ubuntu/linux-intel-5.13*
ubuntu/linux-oem-5.10*
ubuntu/linux-oem-5.13*
ubuntu/linux-oem-5.6*
ubuntu/linux-oracle-5.11*
ubuntu/linux-oracle-5.13*
ubuntu/linux-oracle-5.8*
ubuntu/linux-raspi2*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.11*
ubuntu/linux-riscv-5.8*
ubuntu/linux-allwinner-5.19*
ubuntu/linux-aws-5.19*
ubuntu/linux-aws-6.2*
ubuntu/linux-aws-6.5*
ubuntu/linux-aws-6.8<6.8.0-1066.69~22.04.1
6.8.0-1066.69~22.04.1
ubuntu/linux-azure-5.19*
ubuntu/linux-azure-6.2*
ubuntu/linux-azure-6.5*
ubuntu/linux-azure-6.8<6.8.0-1070.78~22.04.1
6.8.0-1070.78~22.04.1
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-azure-fde-6.8<6.8.0-1068.75~22.04.1
6.8.0-1068.75~22.04.1
ubuntu/linux-gcp-5.19*
ubuntu/linux-gcp-6.2*
ubuntu/linux-gcp-6.5*
ubuntu/linux-gcp-6.8<6.8.0-1070.78~22.04.1
6.8.0-1070.78~22.04.1
ubuntu/linux-hwe-5.19*
ubuntu/linux-hwe-6.2*
ubuntu/linux-hwe-6.5*
ubuntu/linux-ibm-6.8<6.8.0-1066.67~22.04.1
6.8.0-1066.67~22.04.1
ubuntu/linux-intel-iot-realtime*
ubuntu/linux-lowlatency-hwe-5.19*
ubuntu/linux-lowlatency-hwe-6.2*
ubuntu/linux-lowlatency-hwe-6.5*
ubuntu/linux-lowlatency-hwe-6.8<6.8.0-146.146.1~22.04.1
6.8.0-146.146.1~22.04.1
ubuntu/linux-nvidia-6.2*
ubuntu/linux-nvidia-6.5*
ubuntu/linux-nvidia-6.8<6.8.0-1064.67~22.04.1
6.8.0-1064.67~22.04.1
ubuntu/linux-oem-5.17*
ubuntu/linux-oem-6.0*
ubuntu/linux-oem-6.1*
ubuntu/linux-oem-6.5*
ubuntu/linux-oracle-6.5*
ubuntu/linux-oracle-6.8*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-riscv-6.5*
ubuntu/linux-riscv-6.8<6.8.0-146.146~22.04.1
6.8.0-146.146~22.04.1
ubuntu/linux-starfive-5.19*
ubuntu/linux-starfive-6.2*
ubuntu/linux-starfive-6.5*
ubuntu/linux-realtime-6.8<6.8.1-1061.62~22.04.1
6.8.1-1061.62~22.04.1
ubuntu/linux<6.8.0-146.146
6.8.0-146.146
ubuntu/linux-aws<6.8.0-1066.69
6.8.0-1066.69
ubuntu/linux-aws-6.14*
ubuntu/linux-aws-6.17*
ubuntu/linux-azure<6.8.0-1070.78
6.8.0-1070.78
ubuntu/linux-azure-6.11*
ubuntu/linux-azure-6.14*
ubuntu/linux-azure-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-azure-fde<6.8.0-1068.75
6.8.0-1068.75
ubuntu/linux-azure-fde-6.14*
ubuntu/linux-azure-fde-6.17*
ubuntu/linux-azure-fde-7.0<7.0.0-1013.13~24.04.1
7.0.0-1013.13~24.04.1
ubuntu/linux-azure-nvidia*
ubuntu/linux-azure-nvidia-6.14*
ubuntu/linux-gcp<6.8.0-1070.78
6.8.0-1070.78
ubuntu/linux-gcp-6.11*
ubuntu/linux-gcp-6.14*
ubuntu/linux-gcp-7.0<7.0.0-1011.11~24.04.1
7.0.0-1011.11~24.04.1
ubuntu/linux-gke<6.8.0-1065.73
6.8.0-1065.73
ubuntu/linux-gkeop<6.8.0-1051.55
6.8.0-1051.55
ubuntu/linux-hwe-6.11*
ubuntu/linux-hwe-6.14*
ubuntu/linux-hwe-7.0<7.0.0-28.28~24.04.1
7.0.0-28.28~24.04.1
ubuntu/linux-ibm<6.8.0-1066.67
6.8.0-1066.67
ubuntu/linux-lowlatency<6.8.0-146.146.1
6.8.0-146.146.1
ubuntu/linux-lowlatency-hwe-6.11*
ubuntu/linux-nvidia<6.8.0-1064.67
6.8.0-1064.67
ubuntu/linux-nvidia-6.11*
ubuntu/linux-nvidia-7.0<7.0.0-1016.16~24.04.1
7.0.0-1016.16~24.04.1
ubuntu/linux-nvidia-lowlatency<6.8.0-1064.67.1
6.8.0-1064.67.1
ubuntu/linux-nvidia-tegra*
ubuntu/linux-oem-6.11*
ubuntu/linux-oem-6.14*
ubuntu/linux-oem-6.8*
ubuntu/linux-oracle<6.8.0-1063.66
6.8.0-1063.66
ubuntu/linux-oracle-6.14*
ubuntu/linux-oracle-7.0<7.0.0-1011.11~24.04.1
7.0.0-1011.11~24.04.1
ubuntu/linux-raspi*
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-6.14*
ubuntu/linux-riscv-6.17*
ubuntu/linux-riscv-7.0<7.0.0-28.28.1~24.04.3
7.0.0-28.28.1~24.04.3
ubuntu/linux-xilinx*
ubuntu/linux-bluefield<6.8.0-1032.37
6.8.0-1032.37
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime<6.8.1-1061.62
6.8.1-1061.62
ubuntu/linux-realtime-6.14*
ubuntu/linux-aws-fips<6.8.0-1066.69+fips1
6.8.0-1066.69+fips1
ubuntu/linux-azure-fips<6.8.0-1069.77+fips1
6.8.0-1069.77+fips1
ubuntu/linux-fips<6.8.0-146.146+fips1
6.8.0-146.146+fips1
ubuntu/linux-gcp-fips<6.8.0-1070.78+fips1
6.8.0-1070.78+fips1
ubuntu/linux<7.0.0-28.28
7.0.0-28.28
ubuntu/linux-aws<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-azure<7.0.0-1010.10
7.0.0-1010.10
ubuntu/linux-azure-fde<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-gcp<7.0.0-1008.8
7.0.0-1008.8
ubuntu/linux-gke<7.0.0-1003.4
7.0.0-1003.4
ubuntu/linux-ibm<7.0.0-1010.10
7.0.0-1010.10
ubuntu/linux-nvidia<7.0.0-1016.16
7.0.0-1016.16
ubuntu/linux-nvidia-bos<7.0.0-2016.16
7.0.0-2016.16
ubuntu/linux-oem-7.0<7.0.0-1009.9
7.0.0-1009.9
ubuntu/linux-oracle<7.0.0-1008.8
7.0.0-1008.8
ubuntu/linux-raspi<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-realtime<7.0.0-28.28.1
7.0.0-28.28.1
ubuntu/linux-riscv<7.0.0-28.28.1
7.0.0-28.28.1
debian/linux<6.12.94-1
6.12.94-1
debian/linux<7.0.12-1
7.0.12-1
linux/kernel<6.12.93
6.12.93
linux/kernel>=6.13.0<6.18.35
6.18.35
linux/kernel>=6.19.0<7.0.12
7.0.12
debian/linux
6.1.176-16.1.190-16.12.107-16.12.115-27.2.12-17.2.15-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 6.6.159.1-1
  2. Upgrade

    Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69~22.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78~22.04.1
  4. Upgrade

    Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.75~22.04.1
  5. Upgrade

    Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78~22.04.1
  6. Upgrade

    Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.67~22.04.1
  7. Upgrade

    Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146.1~22.04.1
  8. Upgrade

    Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67~22.04.1
  9. Upgrade

    Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146~22.04.1
  10. Upgrade

    Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.1-1061.62~22.04.1
  11. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146
  12. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69
  13. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78
  14. Upgrade

    Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  15. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.75
  16. Upgrade

    Upgrade ubuntu/linux-azure-fde-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13~24.04.1
  17. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78
  18. Upgrade

    Upgrade ubuntu/linux-gcp-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1011.11~24.04.1
  19. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 6.8.0-1065.73
  20. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.55
  21. Upgrade

    Upgrade ubuntu/linux-hwe-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28~24.04.1
  22. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.67
  23. Upgrade

    Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146.1
  24. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67
  25. Upgrade

    Upgrade ubuntu/linux-nvidia-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16~24.04.1
  26. Upgrade

    Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-1064.67.1
  27. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 6.8.0-1063.66
  28. Upgrade

    Upgrade ubuntu/linux-oracle-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1011.11~24.04.1
  29. Upgrade

    Upgrade ubuntu/linux-riscv-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1~24.04.3
  30. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 6.8.0-1032.37
  31. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.1-1061.62
  32. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1066.69+fips1
  33. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.77+fips1
  34. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-146.146+fips1
  35. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1070.78+fips1
  36. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28
  37. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  38. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 7.0.0-1010.10
  39. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  40. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.8
  41. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 7.0.0-1003.4
  42. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 7.0.0-1010.10
  43. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16
  44. Upgrade

    Upgrade ubuntu/linux-nvidia-bos to a version that resolves this vulnerability.

    Fixed in 7.0.0-2016.16
  45. Upgrade

    Upgrade ubuntu/linux-oem-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1009.9
  46. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.8
  47. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  48. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1
  49. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 7.0.0-28.28.1
  50. Upgrade

    Upgrade linux/Kernel to a version that resolves this vulnerability.

    Fixed in 6.12.93
  51. Upgrade

    Upgrade linux/Kernel to a version that resolves this vulnerability.

    Fixed in 6.18.35
  52. Upgrade

    Upgrade linux/Kernel to a version that resolves this vulnerability.

    Fixed in 7.0.12
  53. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.12.94-1
  54. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 7.0.12-1
  55. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.14-1
  56. Compensating control

    Update the Linux kernel XFRM per-network-namespace teardown to use the documented pre_exit/exit split: move the policy flush and dependent workqueue drains into a new pre_exit handler, and run xfrm_policy_fini() in the exit handler so policy_bydst hash tables are freed after cleanup_net()'s inter-phase RCU synchronization.

Event History

Jul 25, 2026
CVE Published
via MITRE·09:20 AM
Data Sourced
via MITRE·09:20 AM
Description
Data Sourced
via OSV·09:20 AM
DescriptionAffected Software
Data Sourced
via NVD·10:17 AM
Description
Jul 26, 2026
Data Sourced
via Microsoft·08:07 AM
DescriptionSeverityWeaknessAffected Software
Jul 27, 2026
Data Sourced
via OSV·12:00 AM
Severity

Frequently Asked Questions

1

What is the severity of CVE-2026-64525?

The severity of CVE-2026-64525 is rated at 55.

2

What software is affected by CVE-2026-64525?

CVE-2026-64525 affects the Linux kernel.

3

How do I fix CVE-2026-64525?

To fix CVE-2026-64525, make sure to update the Linux kernel to the latest version where this vulnerability has been patched.

4

What is the nature of the vulnerability in CVE-2026-64525?

CVE-2026-64525 involves inappropriate handling of RCU synchronization during namespace exit in the Linux kernel.

5

Can CVE-2026-64525 be exploited remotely?

CVE-2026-64525 does not specifically indicate remote exploitability, but vulnerabilities in the kernel can often affect system stability and security.

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