high CVSS 7.1 EPSS <0.1%

CVE-2021-47039·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ataflop: potential out of bounds in do_format() The function uses "type" as an array index: q = unit[drive].disk[type]->queue; Unfortunately the bounds check on "type" isn't done until later in the function. Fix this by moving the bounds check to the start.

Severity
high
Software
Kernel
Fixed in
5.12.4
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-2021-47039 scores 7.1 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: 5.12

Until: 5.12.4

Fixed in: 5.12.4

How to fix this CVE

Update your Linux kernel to version 5.12.4 or later to patch the out-of-bounds array access vulnerability in the ataflop disk driver. This flaw could allow a local privileged user to trigger memory corruption or denial of service. Kernel updates should be applied immediately followed by a system reboot to take effect.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version by running: uname -r
  2. Step 2: Verify if you are affected by checking if your version is between 5.12.0 and 5.12.3: grep VERSION /proc/version
  3. Step 3: Search kernel logs for ataflop-related errors or crashes: sudo dmesg | grep -i ataflop
  4. Step 4: After patching, confirm the new kernel is active: uname -r should show version 5.12.4 or higher

FAQ

What is CVE-2021-47039?

This vulnerability exists in the Linux kernel's ataflop (Atari floppy disk driver) where an array bounds check is performed too late in the do_format() function, allowing an out-of-bounds memory access via the 'type' parameter.

Is CVE-2021-47039 being actively exploited?

No, there is no evidence of active exploitation in the wild, and no public exploits are available for this vulnerability.

What versions of Kernel are affected by CVE-2021-47039?

Linux kernel versions 5.12.0 through 5.12.3 are affected. Version 5.12.4 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47039?

Run 'uname -r' and check if the output shows a kernel version between 5.12.0 and 5.12.3; if so, your system is vulnerable and requires a kernel update.

Does Defensia detect CVE-2021-47039?

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-2021-47039 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-53384CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: serial: 8250_dw: unregister 8250 port if clk_notifier_register() fails dw8250_probe() registers the 8250 port via serial8250_register_8250_port() and then, if the device has a clock, registers a clock notifier. If clk_notifier_register() fails, probe returns the error but leaves the 8250 port registered. The matching serial8250_unregister_port() lives in dw8250_remove(), which is not called when probe fails, so the port slot stays occupied until the device is rebound or the system is rebooted. The devm-allocated driver data is freed while the port still references it (via the saved private_data and serial_in/serial_out callbacks), so any access to that port slot before a rebind is a use-after-free hazard. Unregister the port on the clk_notifier_register() error path.
CVE-2026-52931CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: batman-adv: tp_meter: avoid use of uninit sender vars batadv_tp_recv_ack() and batadv_tp_stop() are only valid for tp_vars in the BATADV_TP_SENDER role. When called with a BATADV_TP_RECEIVER role, it proceeds to read sender-only members that were never initialized, leading to undefined behavior. This can be triggered when a node that is currently acting as a receiver in an ongoing tp_meter session receives a malicious ACK packet. Guard against this by checking tp_vars->role immediately after the lookup and bailing out if it is not BATADV_TP_SENDER, before any of those members are accessed.
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References

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