high CVSS 7.1 EPSS <0.1%

CVE-2024-36931·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: s390/cio: Ensure the copied buf is NUL terminated Currently, we allocate a lbuf-sized kernel buffer and copy lbuf from userspace to that buffer. Later, we use scanf on this buffer but we don't ensure that the string is terminated inside the buffer, this can lead to OOB read when using scanf. Fix this issue by using memdup_user_nul instead.

Severity
high
Software
Kernel
Fixed in
6.8.10
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 17% 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-2024-36931 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: 6.7

Until: 6.8.10

Fixed in: 6.8.10

How to fix this CVE

Update your Linux kernel to version 6.8.10 or later to patch a memory safety issue in the s390/cio subsystem. The vulnerability allows out-of-bounds reads when kernel buffers are not properly null-terminated before string parsing. Apply this update promptly, especially if your infrastructure runs IBM System z architecture systems.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r (ensure version is 6.8.10 or later)
  2. Verify s390/cio driver is compiled: grep -i CONFIG_S390_CIO /boot/config-$(uname -r) | grep -q 'y' && echo 'CIO enabled' || echo 'CIO not enabled'
  3. Search kernel logs for memory access violations: sudo grep -i 'WARNING\|ERROR\|BUG' /var/log/kern.log | grep -i 'cio\|userspace'
  4. After patching, confirm fix: uname -r and verify output shows 6.8.10 or higher

FAQ

What is CVE-2024-36931?

This vulnerability exists in the Linux kernel's s390/cio (Channel I/O) subsystem where a kernel buffer copied from user input lacks proper null-termination, enabling out-of-bounds memory reads when string parsing functions are applied.

Is CVE-2024-36931 being actively exploited?

No, this vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog and has no known public exploits available.

What versions of Kernel are affected by CVE-2024-36931?

Linux kernel versions 6.7 through 6.8.9 are vulnerable. The fix is included in kernel 6.8.10 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2024-36931?

Run 'uname -r' to check your kernel version. If the output is between 6.7 and 6.8.9, your system is vulnerable. For s390/z-series systems specifically, also verify that CONFIG_S390_CIO is enabled in your kernel configuration.

Does Defensia detect CVE-2024-36931?

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-2024-36931 will appear in your dashboard with remediation steps.

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References

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