Vulnary
← back to the feed
Critical· 9.8official fix available

CVE-2025-40258

A race condition in the Linux kernel's MPTCP implementation can cause a use‑after‑free, potentially allowing arbitrary code execution or denial of service. The flaw occurs when mptcp_schedule_work() schedules work and takes a reference count on a socket, but the worker thread may run before the reference is held, leading to a refcount error. This vulnerability has been resolved in the kernel.

publishedDec 4, 2025
last modifiedJul 30, 2026
sourcesNVD
severity · cvss
9.8
critical · how bad it is
exploitation · epss
<1%
37th percentile · chance of exploitation in 30 days
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
auto-deletes from the system
counting…on Aug 29, 2026

An official fix is available, so this entry is kept for 30 days and then removed automatically.

01

Who is affected

Linux systems using the MPTCP subsystem.

02

Real-world impact

An attacker could exploit the race condition to execute arbitrary code or crash the system.

03

Why this severity

CVSS v3.1 base score 9.8 (Critical) due to network‑adjacent attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability.

04

What to do about it

official fix available
recommended steps
  1. 01Upgrade the Linux kernel to a version that includes the fix for the race condition in mptcp_schedule_work() (as referenced in the NVD description).
  2. 02Reboot the system to load the updated kernel.

NVD-referenced vendor advisory

05

Timeline

  1. Dec 4, 2025 · Dec 4, 2025
    Published
    Disclosed and added to the National Vulnerability Database.
  2. Jul 30, 2026 · 6d ago
    Advisory updated
    The NVD record was last revised.
  3. Jul 30, 2026 · 6d ago
    Official fix available
    A vendor patch or mitigation now exists — see the remediation steps above.
06

How it’s attacked

Attack vectorNetwork (remote)
Attack complexityLow
Privileges requiredNone
User interactionNone needed
ScopeUnchanged
Confidentiality impactHigh
Integrity impactHigh
Availability impactHigh
07

References & advisories

NVD advisory ↗Search advisories ↗
(ai-assisted) A model wrote this summary from the official data, so double-check it against the source before you act on it. Read the official advisory →
CVE-2025-40258: A race condition in the Linux kernel's MPTCP implementation can cause · Vulnary