high CVSS 7.8 EPSS <0.1%

CVE-2021-47564·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net: marvell: prestera: fix double free issue on err path fix error path handling in prestera_bridge_port_join() that cases prestera driver to crash (see below). Trace: Internal error: Oops: 96000044 [#1] SMP Modules linked in: prestera_pci prestera uio_pdrv_genirq CPU: 1 PID: 881 Comm: ip Not tainted 5.15.0 #1 pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : prestera_bridge_destroy+0x2c/0xb0 [prestera] lr : prestera_bridge_port_join+0x2cc/0x350 [prestera] sp : ffff800011a1b0f0 ... x2 : ffff000109ca6c80 x1 : dead000000000100 x0 : dead000000000122 Call trace: prestera_bridge_destroy+0x2c/0xb0 [prestera] prestera_bridge_port_join+0x2cc/0x350 [prestera] prestera_netdev_port_event.constprop.0+0x3c4/0x450 [prestera] prestera_netdev_event_handler+0xf4/0x110 [prestera] raw_notifier_call_chain+0x54/0x80 call_netdevice_notifiers_info+0x54/0xa0 __netdev_upper_dev_link+0x19c/0x380

Severity
high
Software
Kernel
Fixed in
5.15.6
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 10% 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-2021-47564 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: 5.11

Until: 5.15.6

Fixed in: 5.15.6

How to fix this CVE

Update your Linux kernel to version 5.15.6 or later to resolve a double-free memory corruption issue in the Marvell Prestera driver's bridge port join error handling path. This vulnerability can cause kernel crashes when network bridge operations fail. Apply the patch immediately to prevent denial-of-service conditions on systems using Marvell Prestera network adapters.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r (vulnerable if output shows 5.11.x through 5.15.5)
  2. Verify Marvell Prestera driver presence: lsmod | grep prestera (if loaded, system is potentially vulnerable)
  3. Search kernel logs for crashes: sudo dmesg | grep -i 'prestera\|oops\|kernel panic' (look for prestera_bridge_destroy or prestera_bridge_port_join in stack traces)
  4. Confirm patch applied: grep 'prestera_bridge_port_join' /boot/System.map and verify kernel version is 5.15.6+ via uname -r

FAQ

What is CVE-2021-47564?

This vulnerability is a double-free memory corruption bug in the Linux kernel's Marvell Prestera network driver that occurs during error handling in bridge port join operations. It can cause kernel panics and system crashes on affected systems.

Is CVE-2021-47564 being actively exploited?

No, CVE-2021-47564 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, the denial-of-service impact makes patching important for system stability.

What versions of Kernel are affected by CVE-2021-47564?

Linux kernel versions 5.11 through 5.15.5 are vulnerable. The vulnerability is fixed in kernel 5.15.6 and later.

How do I check if my server is vulnerable to CVE-2021-47564?

Run: uname -r (if output is 5.11.x-5.15.5, vulnerable) and lsmod | grep prestera (if prestera driver is loaded, the system can be affected).

Does Defensia detect CVE-2021-47564?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47564 will appear in your dashboard with remediation steps.

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References

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