high CVSS 7.8 EPSS <0.1%

CVE-2021-47477·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: comedi: dt9812: fix DMA buffers on stack USB transfer buffers are typically mapped for DMA and must not be allocated on the stack or transfers will fail. Allocate proper transfer buffers in the various command helpers and return an error on short transfers instead of acting on random stack data. Note that this also fixes a stack info leak on systems where DMA is not used as 32 bytes are always sent to the device regardless of how short the command is.

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 19% 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-2021-47477 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 resolve a critical DMA buffer allocation vulnerability in the comedi dt9812 USB driver. This flaw could allow local attackers to leak kernel stack memory or trigger USB transfer failures. Systems running affected kernel versions should prioritize this update to prevent potential privilege escalation or information disclosure.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your current kernel version: uname -r — if it shows 5.15.0 through 5.15.1, your system is vulnerable
  2. Verify if the comedi dt9812 driver is loaded: lsmod | grep dt9812 — if present, the vulnerable component is active
  3. Search kernel logs for DMA-related USB errors: dmesg | grep -i 'usb.*dt9812\|dma' — look for transfer failures or stack data anomalies
  4. After patching, confirm the new kernel version: uname -r should show 5.15.2 or higher, and reboot if necessary

FAQ

What is CVE-2021-47477?

CVE-2021-47477 is a kernel vulnerability in the comedi dt9812 USB driver where DMA transfer buffers were incorrectly allocated on the kernel stack. This can cause USB operations to fail and leak sensitive kernel memory to user-space applications.

Is CVE-2021-47477 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits have been disclosed. However, it still poses a security risk and should be patched promptly.

What versions of Kernel are affected by CVE-2021-47477?

Linux kernel versions 5.15.0 through 5.15.1 are vulnerable. The fix is available in kernel 5.15.2 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2021-47477?

Run uname -r and check the output — if it shows 5.15.0 or 5.15.1, your system is vulnerable. Additionally, run lsmod | grep dt9812 to confirm if the affected driver is loaded.

Does Defensia detect CVE-2021-47477?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47477 will appear in your dashboard with remediation steps.

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References

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