CVE-2025-40186Network attack vector

Kernel memory corruption via request-socket double-free

Published Nov 12, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel TCP Fast Open handling allows remote attackers to crash the kernel through a listener-close race. tcp_conn_request removes the same request socket after tcp_disconnect has already dropped its last reference, causing a refcount underflow and double-free. Exploitation requires a TCP Fast Open SYN to coincide with a local listener close; successful heap corruption can crash the kernel or enable code execution.

CVSS severity8.1
High
EPSS probability0.54%
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

Use-after-free in Linux kernel TCP Fast Open handling allows remote attackers to crash the kernel through a listener-close race. tcp_conn_request removes the same request socket after tcp_disconnect has already dropped its last reference, causing a refcount underflow and double-free. Exploitation requires a TCP Fast Open SYN to coincide with a local listener close; successful heap corruption can crash the kernel or enable code execution.

The record

CVE
CVE-2025-40186
Published
Nov 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record 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=17d699727577814198d744d6afe54735c6b54c99 <643a94b0cf767325e953591c212be2eb826b9d7f
  2. Affected versionversion=33a4fdf0b4a25f8ce65380c3b0136b407ca57609 <eb85ad5f23268d64b037bfb545cbcba3752f90c7
  3. Affected versionversion=45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 <2e7cbbbe3d61c63606994b7ff73c72537afe2e1c
  4. Affected versionversion=45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 <64dc47a13aa3d9daf7cec29b44dca8e22a6aea15
  5. Affected versionversion=5.10.245 <5.10.246
  6. Affected versionversion=5.15.194 <5.15.195
  7. Affected versionversion=5.4.300 <5.4.301
  8. Affected versionversion=6.1.154 <6.1.157
  9. Affected versionversion=6.12.49 <6.12.54
  10. Affected versionversion=6.16.9 <6.17
  11. Affected versionversion=6.17
  12. Affected versionversion=6.6.108 <6.6.113
  13. Affected versionversion=7ec092a91ff351dcde89c23e795b73a328274db6 <e359b742eac1eac75cff4e38ee2e8cea492acd9b
  14. Affected versionversion=a4378dedd6e07e62f2fccb17d78c9665718763d0 <ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d
  15. Affected versionversion=ae313d14b45eca7a6bb29cb9bf396d977e7d28fb
  16. Affected versionversion=dfd06131107e7b699ef1e2a24ed2f7d17c917753 <422c1c173c39bbbae1e0eaaf8aefe40b2596233b
  17. Affected versionversion=fa4749c065644af4db496b338452a69a3e5147d9 <c11ace909e873118295e9eb22dc8c58b0b50eb32

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=17d699727577814198d744d6afe54735c6b54c99 <643a94b0cf767325e953591c212be2eb826b9d7f; version=33a4fdf0b4a25f8ce65380c3b0136b407ca57609 <eb85ad5f23268d64b037bfb545cbcba3752f90c7; version=45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 <2e7cbbbe3d61c63606994b7ff73c72537afe2e1c; version=45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 <64dc47a13aa3d9daf7cec29b44dca8e22a6aea15; version=5.10.245 <5.10.246; version=5.15.194 <5.15.195; version=5.4.300 <5.4.301; version=6.1.154 <6.1.157; version=6.12.49 <6.12.54; version=6.16.9 <6.17; version=6.17; version=6.6.108 <6.6.113; version=7ec092a91ff351dcde89c23e795b73a328274db6 <e359b742eac1eac75cff4e38ee2e8cea492acd9b; version=a4378dedd6e07e62f2fccb17d78c9665718763d0 <ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d; version=ae313d14b45eca7a6bb29cb9bf396d977e7d28fb; version=dfd06131107e7b699ef1e2a24ed2f7d17c917753 <422c1c173c39bbbae1e0eaaf8aefe40b2596233b; version=fa4749c065644af4db496b338452a69a3e5147d9 <c11ace909e873118295e9eb22dc8c58b0b50eb32

Published CVSS scores

8.1Linux kernel CVE teamCVSS:3.1/AV:N/AC:H/PR:N/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

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