medium CVSS 5.5

CVE-2021-47325·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: iommu/arm-smmu: Fix arm_smmu_device refcount leak in address translation The reference counting issue happens in several exception handling paths of arm_smmu_iova_to_phys_hard(). When those error scenarios occur, the function forgets to decrease the refcount of "smmu" increased by arm_smmu_rpm_get(), causing a refcount leak. Fix this issue by jumping to "out" label when those error scenarios occur.

Severity
medium
Software
Kernel
Fixed in
5.13.4
Published
2024-05-21

Affected versions

From: 5.13

Until: 5.13.4

Fixed in: 5.13.4

How to fix this CVE

Update your Linux kernel to version 5.13.4 or later to resolve a reference counting leak in the ARM SMMU IOMMU driver that can cause memory exhaustion and system instability. The vulnerability occurs when the arm_smmu_iova_to_phys_hard() function fails to properly release device references during error conditions. Apply this patch promptly to prevent resource depletion on systems using ARM SMMU-based I/O memory management.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your kernel version: uname -r — vulnerable versions are 5.13.0 through 5.13.3
  2. Verify ARM SMMU driver is loaded: lsmod | grep arm_smmu — if output appears, the vulnerable component is active
  3. Search kernel logs for memory pressure or refcount warnings: sudo dmesg | grep -i 'refcount\|memory\|smmu' — look for warnings about resource exhaustion
  4. After patching, confirm the fix: uname -r should show 5.13.4 or later; verify with sudo dmesg | grep 'smmu' for any remaining errors

FAQ

What is CVE-2021-47325?

This vulnerability is a reference counting leak in the ARM SMMU IOMMU driver where error handling paths fail to release device references, allowing an attacker or buggy code to exhaust kernel memory and degrade system performance or trigger a denial of service.

Is CVE-2021-47325 being actively exploited?

No, this vulnerability is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, it can still be triggered accidentally through I/O memory management operations.

What versions of Kernel are affected by CVE-2021-47325?

Linux kernel versions 5.13.0 through 5.13.3 are affected. The vulnerability was resolved in kernel 5.13.4 and later.

How do I check if my server is vulnerable to CVE-2021-47325?

Run uname -r to check your kernel version — if it shows 5.13.0 to 5.13.3, you are vulnerable. Additionally, run lsmod | grep arm_smmu to confirm if the ARM SMMU driver is active on your system.

Does Defensia detect CVE-2021-47325?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server running a vulnerable version, CVE-2021-47325 will appear in your dashboard with remediation steps.

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References

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