CVE-2025-39686

Kernel-stack disclosure via single-sample Comedi emulation

Published Sep 5, 2025 · Updated Sep 5, 2025

Information disclosure in Linux allows local users to read uninitialized kernel-stack data through multi-sample Comedi INSN_READ requests. The insn_rw_emulate_bits() fallback constructs and processes only one INSN_BITS sample, while the Comedi core returns the requested insn->n samples to user space. Reachability requires a Comedi subdevice with an INSN_BITS handler but no INSN_READ handler; requesting more than one sample can disclose stale stack contents.

CVSS severity7.8
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Information disclosure in Linux allows local users to read uninitialized kernel-stack data through multi-sample Comedi INSN_READ requests. The insn_rw_emulate_bits() fallback constructs and processes only one INSN_BITS sample, while the Comedi core returns the requested insn->n samples to user space. Reachability requires a Comedi subdevice with an INSN_BITS handler but no INSN_READ handler; requesting more than one sample can disclose stale stack contents.

The record

CVE
CVE-2025-39686
Published
Sep 5, 2025
Updated
Sep 5, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 5, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.29
  2. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <7afba9221f70d4cbce0f417c558879cba0eb5e66
  3. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <842f307a1d115b24f2bcb2415c4e344f11f55930
  4. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <92352ed2f9ac422181e381c2430c2d0dfb46faa0
  5. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ab77e85bd3bc006ef40738f26f446a660813da44
  6. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b
  7. Affected versionversion=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <dc0a2f142d655700db43de90cb6abf141b73d908

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.29; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <7afba9221f70d4cbce0f417c558879cba0eb5e66; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <842f307a1d115b24f2bcb2415c4e344f11f55930; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <92352ed2f9ac422181e381c2430c2d0dfb46faa0; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ab77e85bd3bc006ef40738f26f446a660813da44; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b; version=ed9eccbe8970f6eedc1b978c157caf1251a896d4 <dc0a2f142d655700db43de90cb6abf141b73d908

Published CVSS scores

7.8CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo