medium CVSS 5.5 EPSS <0.1%

CVE-2021-47283·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net:sfc: fix non-freed irq in legacy irq mode SFC driver can be configured via modparam to work using MSI-X, MSI or legacy IRQ interrupts. In the last one, the interrupt was not properly released on module remove. It was not freed because the flag irqs_hooked was not set during initialization in the case of using legacy IRQ. Example of (trimmed) trace during module remove without this fix: remove_proc_entry: removing non-empty directory 'irq/125', leaking at least '0000:3b:00.1' WARNING: CPU: 39 PID: 3658 at fs/proc/generic.c:715 remove_proc_entry+0x15c/0x170 ...trimmed... Call Trace: unregister_irq_proc+0xe3/0x100 free_desc+0x29/0x70 irq_free_descs+0x47/0x70 mp_unmap_irq+0x58/0x60 acpi_unregister_gsi_ioapic+0x2a/0x40 acpi_pci_irq_disable+0x78/0xb0 pci_disable_device+0xd1/0x100 efx_pci_remove+0xa1/0x1e0 [sfc] pci_device_remove+0x38/0xa0 __device_release_driver+0x177/0x230 driver_detach+0xcb/0x110 bus_remove_driver+0x58/0xd0 pci_unregister_driver+0x2a/0xb0 efx_exit_module+0x24/0xf40 [sfc] __do_sys_delete_module.constprop.0+0x171/0x280 ? exit_to_user_mode_prepare+0x83/0x1d0 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f9f9385800b ...trimmed...

Severity
medium
Software
Kernel
Fixed in
5.12.11
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 6% 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: 5.12.11

Fixed in: 5.12.11

How to fix this CVE

Update your Linux kernel to version 5.12.11 or later to resolve a resource leak in the SFC network driver's legacy IRQ mode. This patch ensures interrupt handlers are properly released during driver module removal, preventing kernel warnings and system instability. Apply this update as soon as possible to maintain clean interrupt management and prevent cumulative resource exhaustion over time.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your kernel version with 'uname -r' — affected versions are 5.11.x through 5.12.10
  2. Step 2: Verify if the SFC driver is loaded with 'lsmod | grep sfc' — if output appears, the driver is active
  3. Step 3: Search kernel logs for interrupt leak warnings with 'dmesg | grep -i "irq\|proc_entry"' or check '/var/log/kern.log' for 'remove_proc_entry' warnings
  4. Step 4: After patching, confirm the new kernel version with 'uname -r' and validate the SFC driver loads cleanly by checking 'dmesg | tail -20' for absence of IRQ-related errors

FAQ

What is CVE-2021-47283?

CVE-2021-47283 is a resource leak vulnerability in the Linux kernel's SFC Solarflare network driver. When the driver operates in legacy interrupt mode (rather than MSI or MSI-X), a flag tracking allocated interrupts is not set, causing the kernel to fail releasing the IRQ handler during module removal and generating kernel warnings.

Is CVE-2021-47283 being actively exploited?

No, CVE-2021-47283 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. This is a reliability issue rather than a security bypass vulnerability.

What versions of Kernel are affected by CVE-2021-47283?

Linux kernel versions 5.11 through 5.12.10 are affected. The vulnerability is patched in kernel 5.12.11 and later versions.

How do I check if my server is vulnerable to CVE-2021-47283?

Run 'uname -r' and 'lsmod | grep sfc' — if your kernel version is between 5.11 and 5.12.10 and the SFC driver is loaded, your system is vulnerable.

Does Defensia detect CVE-2021-47283?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47283 will appear in your dashboard with remediation steps.

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References

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