medium CVSS 5.5 EPSS <0.1%

CVE-2021-47289·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ACPI: fix NULL pointer dereference Commit 71f642833284 ("ACPI: utils: Fix reference counting in for_each_acpi_dev_match()") started doing "acpi_dev_put()" on a pointer that was possibly NULL. That fails miserably, because that helper inline function is not set up to handle that case. Just make acpi_dev_put() silently accept a NULL pointer, rather than calling down to put_device() with an invalid offset off that NULL pointer.

Severity
medium
Software
Kernel
Fixed in
5.13.6
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 3% 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.

Affected versions

From: 5.11

Until: 5.13.6

Fixed in: 5.13.6

How to fix this CVE

Update your Linux kernel to version 5.13.6 or later to resolve a NULL pointer dereference vulnerability in the ACPI subsystem. This issue can cause a kernel panic or denial of service when the ACPI device matching function incorrectly handles NULL pointer references. Apply the latest kernel patches from your distribution's repository to ensure system stability.

sudo dnf check-update kernel && sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with `uname -r` and verify if it falls between 5.11 and 5.13.5
  2. Step 2: Examine ACPI-related kernel modules by running `lsmod | grep -i acpi` to confirm ACPI subsystem is loaded
  3. Step 3: Search system logs for ACPI errors using `dmesg | grep -i acpi` or `journalctl -b | grep -i acpi` to identify potential NULL pointer dereferences
  4. Step 4: After patching, reboot the system with `sudo reboot` and confirm the new kernel version with `uname -r` to ensure version 5.13.6 or higher is running

FAQ

What is CVE-2021-47289?

This vulnerability is a NULL pointer dereference bug in the Linux kernel's ACPI device matching utility. A previous patch inadvertently introduced improper null pointer handling that could crash the kernel when ACPI functions encounter NULL device pointers.

Is CVE-2021-47289 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and there are no public exploits available. However, it should still be patched to prevent unexpected system crashes.

What versions of Kernel are affected by CVE-2021-47289?

Linux kernel versions 5.11 through 5.13.5 are vulnerable. Version 5.13.6 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47289?

Run `uname -r` to check your kernel version. If the output shows a version between 5.11 and 5.13.5 (inclusive), your system is vulnerable and requires patching.

Does Defensia detect CVE-2021-47289?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47289 will appear in your dashboard with remediation steps.

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References

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