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NVD / CVE Program· CNA Linux

CVE-2025-39684: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.18% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 3cd212e895ca2d58963fdc6422502b10dd3966bb, 868a1b68dcd9f2805bb86aa64862402f785d8c4a, aecf0d557ddd95ce68193a5ee1dc4c87415ff08a; azl3 kernel 6.6.96.2-2 on Azure Linux 3.0 6.6.104.2-1.

Low priority for now. Upgrade to Linux Linux 3cd212e895ca2d58963fdc6422502b10dd3966bb, 868a1b68dcd9f2805bb86aa64862402f785d8c4a, aecf0d557ddd95ce68193a5ee1dc4c87415ff08a; azl3 kernel 6.6.96.2-2 on Azure Linux 3.0 6.6.104.2-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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 `do_insn_ioctl()`. A kernel buffer is allocated to hold `insn->n` samples (each of which is an `unsigned int`). For some instruction types, `insn->n` 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 `insn->n` samples, so that there is an information leak. There is a similar syzbot report for `do_insnlist_ioctl()`, although it does not have a reproducer for it at the time of writing. One culprit is `insn_rw_emulate_bits()` which is used as the handler for `INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have a specific handler for that instruction, but do have an `INSN_BITS` handler. For `INSN_READ` it only fills in at most 1 sample, so if `insn->n` is greater than 1, the remaining `insn->n - 1` samples copied to userspace will be uninitialized kernel data. Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. It never returns an error, even if it fails to fill the buffer. Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure that uninitialized parts of the allocated buffer are zeroed before handling each instruction. Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fix replaced the call to `kmalloc_array()` with `kcalloc()`, but it is not always necessary to clear the whole buffer.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Sep 5, 2025
Updated
Oct 19, 2026
EPSS
0.1% · 7th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • linux linux kernel5.16 and later · before 6.1.149
  • linux linux kernel6.2 and later · before 6.6.103
  • linux linux kernel2.6.29 and later · before 5.15.190
  • linux linux kernel6.13 and later · before 6.16.4
  • linux linux kernel6.7 and later · before 6.12.44
  • linux linux kernel6.17

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.29affected
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before 868a1b68dcd9f2805bb86aa64862402f785d8c4aaffected · git
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before ff4a7c18799c7fe999fa56c5cf276e13866b8c1aaffected · git
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before d84f6e77ebe3359394df32ecd97e0d76a25283dcaffected · git
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before f3b0c9ec54736f3b8118f93a473d22e11ee65743affected · git
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before aecf0d557ddd95ce68193a5ee1dc4c87415ff08aaffected · git
    • ed9eccbe8970f6eedc1b978c157caf1251a896d4 and later · before 3cd212e895ca2d58963fdc6422502b10dd3966bbaffected · git
    • before 2.6.29not affected · semver
    • 5.15.190 and later · up to and including 5.15.*not affected · semver
    • 6.1.149 and later · up to and including 6.1.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.153-16.1.153-1
Debian:13linuxbefore 6.12.48-16.12.48-1
Debian:14linuxbefore 6.16.5-16.16.5-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-39682Sep 5, 2025 · tls: fix handling of zero-length records on the rx_listKEV
    70This week
  • ← EarlierCVE-2025-39683Sep 5, 2025 · tracing: Limit access to parser->buffer when trace_get_user failed
    28Monitor
  • Later →CVE-2025-39685Sep 5, 2025 · comedi: pcl726: Prevent invalid irq number
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux3cd212e895ca2d58963fdc6422502b10dd3966bbVendor (CNA)
Linux Linux868a1b68dcd9f2805bb86aa64862402f785d8c4aVendor (CNA)
Linux Linuxaecf0d557ddd95ce68193a5ee1dc4c87415ff08aVendor (CNA)
Linux Linuxd84f6e77ebe3359394df32ecd97e0d76a25283dcVendor (CNA)
Linux Linuxf3b0c9ec54736f3b8118f93a473d22e11ee65743Vendor (CNA)
Linux Linuxff4a7c18799c7fe999fa56c5cf276e13866b8c1aVendor (CNA)
azl3 kernel 6.6.96.2-2 on Azure Linux 3.06.6.104.2-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.153-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-50302290 days apartHID: core: zero-initialize the report bufferKEV
    52Plan
  • CVE-2026-52989292 days apartnvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
    39Monitor
  • CVE-2026-53225293 days apartsctp: fix uninit-value in __sctp_rcv_asconf_lookup()
    36Monitor
  • CVE-2024-47685319 days apartnetfilter: nf_reject_ipv6: fix nf_reject_ip6_tcphdr_put()
    36Monitor
  • CVE-2026-53170293 days apartaccel/ethosu: reject DMA commands with uninitialized length
    35Monitor
  • CVE-2026-43139243 days apartxfrm6: fix uninitialized saddr in xfrm6_get_saddr()
    34Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-908 · Use of Uninitialized Resource

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records