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Vulnerabilities

Vulnerability · CVE-2025-39684

In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a…

Published Sep 5, 2025 · catalog updated Oct 19, 2026 · linux kernel

Open the advisory

Exploitation likelihood is not on this record for CVE-2025-39684. A missing EPSS score is not a low risk. Compare linux kernel with the linked advisory before you change production.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Medium5.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
cpe debian/debian linux · cpe linux/linux kernel

In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in . A kernel buffer is allocated to hold samples (each of which is an ). For some instruction types, samples are copied back to user-space, unless an error code is being returned. The problem is that not all the instruction handlers that need to return data to userspace fill in the whole samples, so that there is an information leak. There is a similar syzbot report for , although it does not have a reproducer for it at the time of writing. One culprit is which is used as the handler for or instructions for subdevices that do not have a specific handler for that instruction, but do have an handler. For it only fills in at most 1 sample, so if is greater than 1, the remaining samples copied to userspace will be uninitialized kernel data. Another culprit is in the "vm80xx" driver. It never returns an error, even if it fails to fill the buffer. Fix it in and by making sure that uninitialized parts of the allocated buffer are zeroed before handling each instruction. Thanks to Arnaud Lecomte for their fix to . That fix replaced the call to with , but it is not always necessary to clear the whole buffer.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe debian/debian linux11.0
  • cpe linux/linux kernel6.17

How to fix CVE-2025-39684

  • Recommended remediation

    A patch or advisory reference is linked. Open the original publisher for availability by product version.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for CVE-2025-39684. A missing EPSS score is not a low risk. Compare linux kernel with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with debian/debian linux 11.0; linux/linux kernel 6.17. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-908: Use of Uninitialized Resource. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 5, 2025 · NIST NVD

    Detected

    In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in . A kernel buffer is allocated to hold samples (each of which is an ). For some instruction types, samples are copied back to user-space, unless an error code is being returned. The problem is that not all t

  2. Oct 19, 2026 · NIST NVD

    Updated

    In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in . A kernel buffer is allocated to hold samples (each of which is an ). For some instruction types, samples are copied back to user-space, unless an error code is being returned. The problem is that not all t

Sources

  • NIST NVDVulnerability recordCVE-2025-39684

    In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in . A kernel buffer is allocated to hold samples (each of w

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 19, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.