CVE-2025-71126Network attack vector

MPTCP connection hang via fallback reinjection deadlock

Published Jan 14, 2026 · Updated Jan 14, 2026

Improper locking in Linux Kernel MPTCP allows attackers to hang affected connections through fallback-time packet reinjection. After MP_FAIL arrives but before the infinite map is sent, the packet scheduler reinjects data while fallback_lock is already held, and __mptcp_try_fallback attempts to acquire that lock again. The trigger requires an MPTCP fallback in this narrow interval; published assessments disagree on whether access is remote or local and on required privileges.

CVSS severity7.5
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in Linux Kernel MPTCP allows attackers to hang affected connections through fallback-time packet reinjection. After MP_FAIL arrives but before the infinite map is sent, the packet scheduler reinjects data while fallback_lock is already held, and __mptcp_try_fallback attempts to acquire that lock again. The trigger requires an MPTCP fallback in this narrow interval; published assessments disagree on whether access is remote or local and on required privileges.

The record

CVE
CVE-2025-71126
Published
Jan 14, 2026
Updated
Jan 14, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-667, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 14, 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=1d82a8fe6ee4afdc92f4e8808c9dad2a6095bbc5
  2. Affected versionversion=54999dea879fecb761225e28f274b40662918c30 <0ca9fb4335e726dab4f23b3bfe87271d8f005f41
  3. Affected versionversion=5586518bec27666c747cd52aabb62d485686d0bf <0107442e82c0f8d6010e07e6030741c59c520d6e
  4. Affected versionversion=6.16
  5. Affected versionversion=75a4c9ab8a7af0d76b31ccd1188ed178c38b35d2 <252892d5a6a2f163ce18f32716e46fa4da7d4e79
  6. Affected versionversion=f8a1d9b18c5efc76784f5a326e905f641f839894 <50f47c02be419bf0a3ae94c118addf67beef359f
  7. Affected versionversion=f8a1d9b18c5efc76784f5a326e905f641f839894 <ffb8c27b0539dd90262d1021488e7817fae57c42

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1d82a8fe6ee4afdc92f4e8808c9dad2a6095bbc5; version=54999dea879fecb761225e28f274b40662918c30 <0ca9fb4335e726dab4f23b3bfe87271d8f005f41; version=5586518bec27666c747cd52aabb62d485686d0bf <0107442e82c0f8d6010e07e6030741c59c520d6e; version=6.16; version=75a4c9ab8a7af0d76b31ccd1188ed178c38b35d2 <252892d5a6a2f163ce18f32716e46fa4da7d4e79; version=f8a1d9b18c5efc76784f5a326e905f641f839894 <50f47c02be419bf0a3ae94c118addf67beef359f; version=f8a1d9b18c5efc76784f5a326e905f641f839894 <ffb8c27b0539dd90262d1021488e7817fae57c42

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.4Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS: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.

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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

CWE-667Improper Locking
T1499.004Endpoint Denial of Service: Application 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

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Your stack

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