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6.8
CVE-2026-43418: Linux kernel can stall during rapid process creation
CVE-2026-43418 · published 6 months ago
Summary
The Linux kernel versions used in several Canonical cloud images may stop responding when many new processes are started at the same time. This happens because the system assigns internal identifiers to new tasks before they are fully registered, leading to a deadlock. Updating to the latest kernel release from your cloud provider resolves the issue.
What to do
- Update debian linux to version 6.19.10-1.
- Update linux kernel to version 6.19.9.
- Update linux linux_kernel to version 6.19.9 or later.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Ubuntu:18.04:LTS | canonical | linux-azure-edge | All versions |
| Ubuntu:18.04:LTS | canonical | linux-gcp-5.3 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-gke-4.15 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-gke-5.4 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-gkeop-5.4 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-hwe | All versions |
| Ubuntu:18.04:LTS | canonical | linux-hwe-edge | All versions |
| Ubuntu:18.04:LTS | canonical | linux-oem | All versions |
| Ubuntu:18.04:LTS | canonical | linux-oracle-5.0 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-oracle-5.3 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-aws-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-aws-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-aws-5.8 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-azure-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-azure-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-azure-5.8 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-azure-fde | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gcp-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gcp-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gcp-5.8 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gke | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gke-5.15 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gkeop | All versions |
| Ubuntu:20.04:LTS | canonical | linux-gkeop-5.15 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-hwe-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-hwe-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-hwe-5.8 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-intel-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oem-5.10 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oem-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oem-5.14 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oem-5.6 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oracle-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oracle-5.13 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-oracle-5.8 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-raspi2 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-riscv | All versions |
| Ubuntu:20.04:LTS | canonical | linux-riscv-5.11 | All versions |
| Ubuntu:20.04:LTS | canonical | linux-riscv-5.8 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-allwinner-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-aws-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-aws-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-aws-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-azure-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-azure-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-azure-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-azure-fde-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-azure-fde-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-gcp-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-gcp-6.2 | All versions |
Showing 50 of 101. Show the rest
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Ubuntu:22.04:LTS | canonical | linux-gcp-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-hwe-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-hwe-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-hwe-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-intel-iot-realtime | All versions |
| Ubuntu:24.04:LTS | canonical | linux-gcp-6.11 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-gcp-6.14 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-hwe-6.11 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-hwe-6.14 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-lowlatency-hwe-6.11 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-nvidia-6.11 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-oem-6.11 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-oem-6.14 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-oem-6.8 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-oracle-6.14 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-raspi-realtime | All versions |
| Ubuntu:24.04:LTS | canonical | linux-realtime | All versions |
| Ubuntu:24.04:LTS | canonical | linux-riscv | All versions |
| Ubuntu:24.04:LTS | canonical | linux-riscv-6.14 | All versions |
| Ubuntu:Pro:Realtime:24.04:LTS | canonical | linux-realtime-6.14 | All versions |
| Ubuntu:26.04:LTS | canonical | linux-azure-fde | All versions |
| Debian:14 | debian | linux |
< 6.19.10-1 Fix: upgrade to 6.19.10-1
|
| Ubuntu:16.04:LTS | canonical | linux-hwe-edge | All versions |
| Ubuntu:18.04:LTS | canonical | linux-aws-5.0 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-aws-5.3 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-azure | All versions |
| Ubuntu:18.04:LTS | canonical | linux-azure-5.3 | All versions |
| Ubuntu:18.04:LTS | canonical | linux-gcp | All versions |
| Ubuntu:22.04:LTS | canonical | linux-lowlatency-hwe-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-lowlatency-hwe-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-lowlatency-hwe-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-nvidia-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-nvidia-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-oem-5.17 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-oem-6.0 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-oem-6.1 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-oem-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-oracle-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-realtime | All versions |
| Ubuntu:22.04:LTS | canonical | linux-riscv | All versions |
| Ubuntu:22.04:LTS | canonical | linux-riscv-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-riscv-6.5 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-starfive-5.19 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-starfive-6.2 | All versions |
| Ubuntu:22.04:LTS | canonical | linux-starfive-6.5 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-aws-6.14 | All versions |
| Ubuntu:24.04:LTS | canonical | linux-azure-6.11 | All versions |
| Ubuntu:Nvidia-BlueField:24.04:LTS | canonical | linux-bluefield | All versions |
| Ubuntu:24.04:LTS | canonical | linux-azure-fde-7.0 | All versions |
| – | linux | linux_kernel |
>= 6.19, < 6.19.9 7.0 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Linux | linux | kernel |
>= 6.19.0, < 6.19.9 Fix: upgrade to 6.19.9
|
Original advisory text
sched/mmcid: Prevent CID stalls due to concurrent forks
In the Linux kernel, the following vulnerability has been resolved:
sched/mmcid: Prevent CID stalls due to concurrent forks
A newly forked task is accounted as MMCID user before the task is visible
in the process' thread list and the global task list. This creates the
following problem:
CPU1 CPU2
fork()
sched_mm_cid_fork(tnew1)
tnew1->mm.mm_cid_users++;
tnew1->mm_cid.cid = getcid()
-> preemption
fork()
sched_mm_cid_fork(tnew2)
tnew2->mm.mm_cid_users++;
// Reaches the per CPU threshold
mm_cid_fixup_tasks_to_cpus()
for_each_other(current, p)
....
As tnew1 is not visible yet, this fails to fix up the already allocated CID
of tnew1. As a consequence a subsequent schedule in might fail to acquire a
(transitional) CID and the machine stalls.
Move the invocation of sched_mm_cid_fork() after the new task becomes
visible in the thread and the task list to prevent this.
This also makes it symmetrical vs. exit() where the task is removed as CID
user before the task is removed from the thread and task lists.
sched/mmcid: Prevent CID stalls due to concurrent forks
A newly forked task is accounted as MMCID user before the task is visible
in the process' thread list and the global task list. This creates the
following problem:
CPU1 CPU2
fork()
sched_mm_cid_fork(tnew1)
tnew1->mm.mm_cid_users++;
tnew1->mm_cid.cid = getcid()
-> preemption
fork()
sched_mm_cid_fork(tnew2)
tnew2->mm.mm_cid_users++;
// Reaches the per CPU threshold
mm_cid_fixup_tasks_to_cpus()
for_each_other(current, p)
....
As tnew1 is not visible yet, this fails to fix up the already allocated CID
of tnew1. As a consequence a subsequent schedule in might fail to acquire a
(transitional) CID and the machine stalls.
Move the invocation of sched_mm_cid_fork() after the new task becomes
visible in the thread and the task list to prevent this.
This also makes it symmetrical vs. exit() where the task is removed as CID
user before the task is removed from the thread and task lists.
References
- https://security-tracker.debian.org/tracker/CVE-2026-43418 Vendor Advisory
- https://ubuntu.com/security/CVE-2026-43418 Third Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2026-43418 Third Party Advisory
- https://git.kernel.org/linus/b2e48c429ec54715d16fefa719dd2fbded2e65be Third Party Advisory
- https://git.kernel.org/stable/c/b2e48c429ec54715d16fefa719dd2fbded2e65be URL
- https://git.kernel.org/stable/c/f0189d49282e0458f3a737bd486c1ec048148f66 URL
- https://docs.bell-sw.com/security/cves/CVE-2026-43418 Vendor Advisory
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43418... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-43418 Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git Product
Internet-facing
60 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker partial control (estimated)
Severity
6.8
Medium
Timeline
Published8 May 2026
Updated26 Oct 2026
First seen8 May 2026
Sources
BELL-CVE-2026-43418 · OSV
DEBIAN-CVE-2026-43418 · OSV
CVE-2026-43418 · NVD
UBUNTU-CVE-2026-43418 · OSV
CVE-2026-43418 · OSV
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