high CVSS 7.8 EPSS <0.1%

CVE-2021-47474·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: comedi: vmk80xx: fix bulk-buffer overflow The driver is using endpoint-sized buffers but must not assume that the tx and rx buffers are of equal size or a malicious device could overflow the slab-allocated receive buffer when doing bulk transfers.

Severity
high
Software
Kernel
Fixed in
5.15.2
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 4% 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-2021-47474 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: 5.15

Until: 5.15.2

Fixed in: 5.15.2

How to fix this CVE

Update your Linux kernel to version 5.15.2 or later to patch a buffer overflow vulnerability in the comedi vmk80xx driver. This vulnerability could allow a local attacker with low privileges to trigger memory corruption by exploiting mismatched transmit and receive buffer sizes during bulk USB transfers. Immediate patching is recommended for systems using USB measurement or data acquisition devices with the comedi driver.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check kernel version with `uname -r` and verify it is 5.15.2 or later
  2. Step 2: Confirm comedi driver is loaded with `lsmod | grep comedi` and check if vmk80xx module is present via `lsmod | grep vmk80xx`
  3. Step 3: Review kernel logs for USB bulk transfer errors using `dmesg | grep -i 'vmk80xx\|comedi\|overflow'` or check `/var/log/kern.log` for buffer overflow warnings
  4. Step 4: After patching, reboot the system and verify the new kernel version with `uname -r` to confirm the fix is active

FAQ

What is CVE-2021-47474?

CVE-2021-47474 is a buffer overflow vulnerability in the Linux kernel's comedi vmk80xx USB driver that arises from unsafe assumptions about endpoint buffer sizes. A local attacker could trigger a slab allocation overflow by connecting a malicious USB device, leading to kernel memory corruption and potential privilege escalation.

Is CVE-2021-47474 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and has no public exploits available, though it remains a high-severity local privilege escalation risk.

What versions of Kernel are affected by CVE-2021-47474?

Linux kernel versions 5.15 through 5.15.1 are affected. The vulnerability is patched in kernel 5.15.2 and later.

How do I check if my server is vulnerable to CVE-2021-47474?

Run `uname -r` to check your kernel version. If it reports a version between 5.15 and 5.15.1, and `lsmod | grep vmk80xx` shows the driver is loaded, your system is vulnerable.

Does Defensia detect CVE-2021-47474?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47474 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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References

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