high CVSS 7.8 EPSS <0.1%

CVE-2022-48892·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: sched/core: Fix use-after-free bug in dup_user_cpus_ptr() Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems"), the setting and clearing of user_cpus_ptr are done under pi_lock for arm64 architecture. However, dup_user_cpus_ptr() accesses user_cpus_ptr without any lock protection. Since sched_setaffinity() can be invoked from another process, the process being modified may be undergoing fork() at the same time. When racing with the clearing of user_cpus_ptr in __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and possibly double-free in arm64 kernel. Commit 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask") fixes this problem as user_cpus_ptr, once set, will never be cleared in a task's lifetime. However, this bug was re-introduced in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in do_set_cpus_allowed(). This time, it will affect all arches. Fix this bug by always clearing the user_cpus_ptr of the newly cloned/forked task before the copying process starts and check the user_cpus_ptr state of the source task under pi_lock. Note to stable, this patch won't be applicable to stable releases. Just copy the new dup_user_cpus_ptr() function over.

Severity
high
Software
Kernel
Fixed in
6.1.7
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 5% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2022-48892 scores 7.8 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 5.16

Until: 6.1.7

Fixed in: 6.1.7

How to fix this CVE

Update your Linux kernel to version 6.1.7 or later to patch a use-after-free vulnerability in the CPU affinity scheduler code. This issue affects kernel versions 5.16 through 6.1.6 and can be triggered when CPU affinity changes race with process forking. Immediate patching is recommended for production systems, particularly ARM64-based deployments where the vulnerability window is larger.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check current kernel version: uname -r — compare against affected range 5.16.x through 6.1.6
  2. Verify vulnerable scheduler code is present: grep -r 'dup_user_cpus_ptr' /boot/config-$(uname -r) || echo 'CONFIG_SMP not found'
  3. Monitor for race condition indicators: dmesg | grep -i 'use.after.free\|double.free\|sanitizer' for KASAN/MSAN detections
  4. Confirm patch applied: grep 'b22faa21b6230d5eccd233e1b7e0026a5002b287' /proc/version_signature || uname -r | grep -E '^6\.1\.([7-9]|[1-9][0-9])' — if not found, system remains vulnerable

FAQ

What is CVE-2022-48892?

CVE-2022-48892 is a use-after-free and potential double-free vulnerability in the Linux kernel's CPU affinity scheduler code. It occurs when process forking races with CPU affinity changes, particularly affecting ARM64 systems where the vulnerability is more easily triggered due to lock protection mechanisms.

Is CVE-2022-48892 being actively exploited?

No, CVE-2022-48892 is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no public exploits are available. However, the high CVSS score (7.8) and local attack vector warrant proactive patching.

What versions of Kernel are affected by CVE-2022-48892?

Linux kernel versions 5.16.0 through 6.1.6 are vulnerable. Version 6.1.7 and later contain the fix. Systems running older kernel branches (5.15 and below) are unaffected.

How do I check if my server is vulnerable to CVE-2022-48892?

Run 'uname -r' and check if the version falls within 5.16.x to 6.1.6 range. Vulnerable examples: 5.16.0, 6.0.12, 6.1.0-6.1.6. Fixed examples: 6.1.7, 6.2.x, 5.15.x (unaffected), 5.14.x (unaffected).

Does Defensia detect CVE-2022-48892?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Linux kernel is installed on a monitored server, CVE-2022-48892 will appear in your dashboard with remediation steps.

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References

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