CVE-2026-97568Network attack vector

MPTCP subflow misclassification via uninitialized backup flag

Published Sep 25, 2026 · Updated Sep 25, 2026

Uninitialized-value use in the Linux kernel allows remote attackers to misclassify an MPTCP subflow through MP_JOIN SYN-cookie processing. In net/mptcp/syncookies.c, SYN-cookie reconstruction leaves the request backup bit uninitialized, and subflow_ulp_clone() copies that indeterminate bit into the new subflow context. Reachability requires an MPTCP listener to process MP_JOIN while SYN cookies are in use; the public fix identifies incorrect backup-path state but documents no further consequence.

CVSS severityUnavailable
Unscored
EPSS probability0.21%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uninitialized-value use in the Linux kernel allows remote attackers to misclassify an MPTCP subflow through MP_JOIN SYN-cookie processing. In net/mptcp/syncookies.c, SYN-cookie reconstruction leaves the request backup bit uninitialized, and subflow_ulp_clone() copies that indeterminate bit into the new subflow context. Reachability requires an MPTCP listener to process MP_JOIN while SYN cookies are in use; the public fix identifies incorrect backup-path state but documents no further consequence.

The record

CVE
CVE-2026-97568
Published
Sep 25, 2026
Updated
Sep 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=09176f80995105c62939728fbad5c437d61e7ff4
  2. Affected versionversion=1008f2bcbc8e461c1df3aebba30ac4f616ebe570
  3. Affected versionversion=5.10.224 <5.11
  4. Affected versionversion=5.15.165 <5.16
  5. Affected versionversion=6.10.4 <6.11
  6. Affected versionversion=6.11
  7. Affected versionversion=6.1.104 <6.2
  8. Affected versionversion=6.6.45 <6.7
  9. Affected versionversion=6f01f41b6a492ddf2da7609967cfaf57e7ca48a7
  10. Affected versionversion=73e2baa301ee3f62ff971e68877adeb37f98cc67
  11. Affected versionversion=8ed3e34c766e8264d5d2e0436f86c51604d6a8a7
  12. Affected versionversion=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <00b2bd518911e0daab00f4749cce68c191ccebb4
  13. Affected versionversion=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <06d649f9cd03a9f8e768a658b20acf8d2c8022e0
  14. Affected versionversion=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <61178d0b85b4b1b53e78b06e89d018d22d102f88
  15. Affected versionversion=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <b76c0e28b392620dfbaf92cdeedbf115820b44cb

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=09176f80995105c62939728fbad5c437d61e7ff4; version=1008f2bcbc8e461c1df3aebba30ac4f616ebe570; version=5.10.224 <5.11; version=5.15.165 <5.16; version=6.10.4 <6.11; version=6.11; version=6.1.104 <6.2; version=6.6.45 <6.7; version=6f01f41b6a492ddf2da7609967cfaf57e7ca48a7; version=73e2baa301ee3f62ff971e68877adeb37f98cc67; version=8ed3e34c766e8264d5d2e0436f86c51604d6a8a7; version=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <00b2bd518911e0daab00f4749cce68c191ccebb4; version=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <06d649f9cd03a9f8e768a658b20acf8d2c8022e0; version=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <61178d0b85b4b1b53e78b06e89d018d22d102f88; version=efd340bf3d7779a3a8ec954d8ec0fb8a10f24982 <b76c0e28b392620dfbaf92cdeedbf115820b44cb

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

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No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
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

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Your stack

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