CVE-2025-39816

Local kernel hang via mutable buffer lengths

Published Sep 16, 2025 · Updated Sep 16, 2025

Race condition in Linux kernel 6.12 io_uring provided buffers allows local users to hang the system through mutable ring lengths. In io_uring/kbuf.c, the kernel rereads a userspace-mapped buffer length after validation, and its incremental commit loop does not stop when that length becomes zero. A low-privileged local process must control the provided-buffer ring; successful exploitation interrupts availability without reported data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.14%
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

Race condition in Linux kernel 6.12 io_uring provided buffers allows local users to hang the system through mutable ring lengths. In io_uring/kbuf.c, the kernel rereads a userspace-mapped buffer length after validation, and its incremental commit loop does not stop when that length becomes zero. A low-privileged local process must control the provided-buffer ring; successful exploitation interrupts availability without reported data disclosure or modification.

The record

CVE
CVE-2025-39816
Published
Sep 16, 2025
Updated
Sep 16, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=6.12
  2. Affected versionversion=ae98dbf43d755b4e111fcd086e53939bef3e9a1a <390a61d284e1ced088d43928dfcf6f86fffdd780
  3. Affected versionversion=ae98dbf43d755b4e111fcd086e53939bef3e9a1a <98b6fa62c84f2e129161e976a5b9b3cb4ccd117b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=6.12; version=ae98dbf43d755b4e111fcd086e53939bef3e9a1a <390a61d284e1ced088d43928dfcf6f86fffdd780; version=ae98dbf43d755b4e111fcd086e53939bef3e9a1a <98b6fa62c84f2e129161e976a5b9b3cb4ccd117b

Published CVSS scores

6.1OracleCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CISACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

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