Description
In the Linux kernel, the following vulnerability has been resolved:
xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit
The struct pernet_operations docstring in include/net/net_namespace.h
explicitly warns against blocking RCU primitives in .exit handlers:
Exit methods using blocking RCU primitives, such as
synchronize_rcu(), should be implemented via exit_batch.
[...]
Please, avoid synchronize_rcu() at all, where it's possible.
Note that a combination of pre_exit() and exit() can
be used, since a synchronize_rcu() is guaranteed between
the calls.
xfrm_policy_fini() violates this: it calls synchronize_rcu() before
freeing the policy_bydst hash tables (so no RCU reader is mid-
traversal at free time), but runs from xfrm_net_ops.exit -- once per
namespace -- so a cleanup_net() of N namespaces pays N full RCU
grace periods serially.
Use the documented pre_exit/exit split. Move the policy flush (and
the workqueue drains it depends on) into a new .pre_exit handler;
xfrm_policy_fini() then runs in .exit and frees the hash tables
after the synchronize_rcu_expedited() that cleanup_net() 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(CLONE_NEWNET)
at ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread
both stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct
net accumulated in the cleanup queue, Percpu in /proc/meminfo climbed
to 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and
__put_net counts were balanced, ruling out a refcount leak.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 6.12.83 – < 6.12.93, 6.18.24 – < 6.18.35, 6.1.191 – < 6.2, 6.6.136 – < 6.7, 6.19.14 – < 6.20, 7.0 | 6.12.93 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 7.0.12-1 | — |
| Debian 13 | linux | 6.12.94-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 24.04 LTS | linux-bluefield | 6.8.0-1032.37 | — |
| Ubuntu 26.04 LTS | linux | 7.0.0-28.28 | — |
| Ubuntu 26.04 LTS | linux-aws +2 | 7.0.0-1009.9 | USN-8618-1 |
| Ubuntu 26.04 LTS | linux-gcp +1 | 7.0.0-1008.8 | — |
| Ubuntu 26.04 LTS | linux-gke | 7.0.0-1003.4 | — |
| Ubuntu 26.04 LTS | linux-ibm +1 | 7.0.0-1010.10 | — |
| Ubuntu 26.04 LTS | linux-nvidia | 7.0.0-1016.16 | USN-8663-1 |
| Ubuntu 26.04 LTS | linux-nvidia-bos | 7.0.0-2016.16 | USN-8664-1 |
| Ubuntu 26.04 LTS | linux-raspi | 7.0.0-1015.15 | USN-8618-1 |
| Ubuntu 26.04 LTS | linux-riscv +1 | 7.0.0-28.28.1 | — |
| Ubuntu 24.04 LTS | linux | 6.8.0-146.146 | USN-8903-1 |
| Ubuntu 24.04 LTS | linux-aws | 6.8.0-1066.69 | USN-8903-1 |
| Ubuntu 24.04 LTS | linux-azure-7.0 | 7.0.0-1014.14~24.04.1 | USN-8728-2 |
| Ubuntu 24.04 LTS | linux-azure-fde | 6.8.0-1068.75 | USN-8904-1 |
| Ubuntu 24.04 LTS | linux-azure-fde-7.0 | 7.0.0-1013.13~24.04.1 | — |
| Ubuntu 24.04 LTS | linux-gcp +1 | 6.8.0-1070.78 | USN-8905-2, USN-8904-1 |
| Ubuntu 24.04 LTS | linux-gcp-7.0 +1 | 7.0.0-1011.11~24.04.1 | USN-8728-3, USN-8728-1 |
| Ubuntu 24.04 LTS | linux-gke | 6.8.0-1065.73 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-gkeop | 6.8.0-1051.55 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-hwe-7.0 | 7.0.0-28.28~24.04.1 | — |
| Ubuntu 24.04 LTS | linux-ibm | 6.8.0-1066.67 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-lowlatency | 6.8.0-146.146.1 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-nvidia | 6.8.0-1064.67 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-nvidia-7.0 | 7.0.0-1016.16~24.04.1 | USN-8663-1 |
| Ubuntu 24.04 LTS | linux-nvidia-lowlatency | 6.8.0-1064.67.1 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-nvidia-tegra | 6.8.0-1038.42 | USN-9002-1 |
| Ubuntu 24.04 LTS | linux-oracle | 6.8.0-1063.66 | USN-8903-2 |
| Ubuntu 24.04 LTS | linux-raspi | 6.8.0-1068.72 | USN-9025-1 |
| Ubuntu 24.04 LTS | linux-riscv +23 | No fix yet | — |
| Ubuntu 24.04 LTS | linux-riscv-7.0 | 7.0.0-28.28.1~24.04.3 | — |
| Ubuntu 22.04 LTS | linux-aws-6.8 | 6.8.0-1066.69~22.04.1 | USN-8903-1 |
| Ubuntu 22.04 LTS | linux-azure-fde-6.8 | 6.8.0-1068.75~22.04.1 | USN-8904-1 |
| Ubuntu 22.04 LTS | linux-gcp-6.8 +1 | 6.8.0-1070.78~22.04.1 | USN-8905-1, USN-8904-1 |
| Ubuntu 22.04 LTS | linux-hwe-6.8 | 6.8.0-149.149~22.04.1 | USN-9066-1 |
| Ubuntu 22.04 LTS | linux-ibm-6.8 | 6.8.0-1066.67~22.04.1 | USN-8906-1 |
| Ubuntu 22.04 LTS | linux-lowlatency-hwe-6.8 | 6.8.0-146.146.1~22.04.1 | USN-8903-2 |
| Ubuntu 22.04 LTS | linux-nvidia-6.8 | 6.8.0-1064.67~22.04.1 | USN-8903-2 |
| Ubuntu 22.04 LTS | linux-oracle-6.8 | 6.8.0-1067.71~22.04.1 | USN-9025-1 |
| Ubuntu 22.04 LTS | linux-riscv +32 | No fix yet | — |
| Ubuntu 22.04 LTS | linux-riscv-6.8 | 6.8.0-146.146~22.04.1 | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu Pro Realtime 24.04 LTS | linux-raspi-realtime | 6.8.0-2056.58 | USN-9025-1 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime | 6.8.1-1061.62 | USN-8903-1 |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime-6.14 | No fix yet | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime-6.8 | 6.8.1-1061.62~22.04.1 | USN-8903-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-aws-fips | 6.8.0-1066.69+fips1 | USN-8903-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-azure-fips | 6.8.0-1069.77+fips1 | USN-8904-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-fips | 6.8.0-146.146+fips1 | USN-8903-1 |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-gcp-fips | 6.8.0-1070.78+fips1 | USN-8905-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | kernel-64kb +7 | 6.4.0-150700.53.90.1 | SUSE-SU-2026:5091-1 |
| SLES 15 SP7 | kernel-default-base | 6.4.0-150700.53.90.1.150700.17.51.1 | SUSE-SU-2026:5091-1 |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | kernel-64kb +8 | 6.12.0-160000.38.1 | SUSE-SU-2026:23902-1 |
| SLES for SAP 16.0 | kernel-default-base | 6.12.0-160000.38.1.160000.2.23 | SUSE-SU-2026:23902-1 |
| SLES 16.0 | kernel-64kb +8 | 6.12.0-160000.38.1 | SUSE-SU-2026:23902-1, SUSE-SU-2026:23897-1 |
| SLES 16.0 | kernel-default-base | 6.12.0-160000.38.1.160000.2.23 | SUSE-SU-2026:23902-1 |
| SLE Micro 6.2 | kernel-default-base | 6.12.0-160000.38.1.160000.2.23 | SUSE-SU-2026:23887-1 |
| SLE Micro 6.2 | kernel-rt +5 | 6.12.0-160000.38.1 | SUSE-SU-2026:23887-1, SUSE-SU-2026:23881-1 |
| SLE Micro 6.1 | kernel-default-base | 6.4.0-159998.55.1.159998.21.41 | SUSE-SU-2026:24619-1 |
| SLE Micro 6.1 | kernel-source +2 | 6.4.0-159998.55.1 | SUSE-SU-2026:24619-1 |
| SLE Micro 6.0 | kernel-default-base | 6.4.0-159998.55.1.159998.21.42 | SUSE-SU-2026:24550-1 |
| SLE Micro 6.0 | kernel-source +2 | 6.4.0-159998.55.1 | SUSE-SU-2026:24550-1 |
| SLE Live Patching 15 SP7 | kernel-default | 6.4.0-150700.53.90.1 | SUSE-SU-2026:5091-1 |
| SLE Live Patching 15 SP7 | kernel-livepatch-SLE15-SP7_Update_24 | 1-150700.15.3.1 | SUSE-SU-2026:5091-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | kernel-default-base | 6.12.0-160000.38.1.160000.2.22 | openSUSE-SU-2026:21910-1 |
| openSUSE Leap 16.0 | kernel-rt +11 | 6.12.0-160000.38.1 | openSUSE-SU-2026:21910-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | kernel-livepatch-6.18.35-68.127 +1 | 1:1.0-0.amzn2023 | ALAS2023-2026-1968, ALAS2023-2026-1881 |
| Amazon Linux 2023 | perf6.12 +11 | 1:6.12.94-123.174.amzn2023 | ALAS2023-2026-1968 |
| Amazon Linux 2023 | perf6.18 +12 | 1:6.18.35-68.127.amzn2023 | ALAS2023-2026-1881 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | kernel | No fix yet | — |
Advisories 26
- USN-9025-1 linux-oracle-6.8, linux-raspi, linux-raspi-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- USN-8903-2 linux-gke, linux-gkeop, linux-ibm, linux-lowlatency, linux-lowlatency-hwe-6.8, linux-nvidia, linux-nvidia-6.8, linux-nvidia-lowlatency, linux-oracle vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- USN-8903-1 linux, linux-aws, linux-aws-6.8, linux-aws-fips, linux-fips, linux-realtime, linux-realtime-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- USN-9066-1 linux-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- USN-8663-1 linux-nvidia, linux-nvidia-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- USN-8728-1 linux-gcp-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- WID-SEC-2026-2527 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- SUSE-SU-2026:24619-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Nov 12, 2026
- USN-8728-2 linux-azure-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
- USN-9002-1 linux-nvidia-tegra vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
- USN-8728-3 linux-oracle-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
- USN-8904-1 linux-azure, linux-azure-6.8, linux-azure-fde, linux-azure-fde-6.8, linux-azure-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8905-2 linux-gcp vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8905-1 linux-gcp-6.8, linux-gcp-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8906-1 linux-ibm-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8664-1 linux-nvidia-bos vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- USN-8618-1 linux-aws, linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
- SUSE-SU-2026:24550-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Nov 6, 2026
- SUSE-SU-2026:5091-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Nov 4, 2026
- SUSE-SU-2026:23902-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Sep 30, 2026
- SUSE-SU-2026:23897-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Sep 30, 2026
- SUSE-SU-2026:23881-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Sep 30, 2026
- SUSE-SU-2026:23887-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Sep 30, 2026
- openSUSE-SU-2026:21910-1 Security update for the Linux Kernel SUSE / openSUSE Security Updates · Sep 25, 2026
- ALAS2023-2026-1968 Important: kernel6.12 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 12, 2026
- ALAS2023-2026-1881 Important: kernel6.18 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Aug 12, 2026