Security readout for executives and security teams
Plain-English summary
A Linux Multipath TCP (MPTCP) locking flaw can freeze affected networking activity when fallback and packet reinjection overlap. Its documented impact is loss of availability, not data theft or modification. Systems that do not use MPTCP are less likely to encounter the vulnerable path.
Executive priority
Treat this as a high-priority availability issue where MPTCP supports exposed or business-critical services. Patch those systems through normal emergency maintenance. For fleets without MPTCP use, verify exposure first and schedule the vendor kernel update according to operational risk.
Technical view
During MPTCP fallback after MP_FAIL, the packet scheduler can attempt reinjection while fallback_lock is already held. This recursively acquires the same lock and deadlocks. The kernel fix prevents reinjection during this critical fallback state. CVSS 3.1 is 7.5: network-accessible, low complexity, no privileges or user interaction, with availability impact only.
Likely exposure
Exposure is concentrated in Linux systems running an affected kernel and actively using MPTCP. Triggering requires the documented fallback and reinjection sequence. The bundle's version representation is ambiguous, so package versions should be verified against distribution guidance and the referenced stable-kernel fixes rather than inferred from version numbers alone.
Exploitation context
CISA KEV status is false, and the supplied sources provide no evidence of active exploitation or a public weaponized exploit. The CVSS vector describes a network-reachable denial-of-service condition, but the bundle does not establish how reliably an unauthenticated remote party can force the required MPTCP state.
Researcher notes
The observed defect is a fallback_lock recursive acquisition reached from retransmission and fallback processing. The stated correction suppresses reinjection only in the critical fallback scenario. No confidentiality or integrity impact is documented. Precise vulnerable release boundaries and remote trigger reliability cannot be established confidently from this bundle alone.
Mitigation direction
- Install a vendor-supported kernel release that incorporates the applicable referenced stable-kernel fix.
- Check Linux distribution advisories for corrected package versions and required reboot instructions.
- Prioritize internet-facing or availability-critical systems that actively use MPTCP.
- If patching is delayed, consult vendor guidance for supported MPTCP exposure-reduction measures.
Validation and detection
- Inventory running kernel and distribution package versions across Linux systems.
- Determine whether MPTCP is enabled and used by exposed or critical workloads.
- Map installed kernels to distribution advisories or the referenced stable fix commits.
- After updating and rebooting, confirm the running kernel is the corrected build.
- Review kernel logs for MPTCP lock warnings, recursive locking reports, or unexplained networking stalls.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2025-71126 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6LinuxVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/0107442e82c0f8d6010e07e6030741c59c520d6eCVE reference, Linux
- https://git.kernel.org/stable/c/252892d5a6a2f163ce18f32716e46fa4da7d4e79CVE reference, Linux
- https://git.kernel.org/stable/c/0ca9fb4335e726dab4f23b3bfe87271d8f005f41CVE reference, Linux
- https://git.kernel.org/stable/c/50f47c02be419bf0a3ae94c118addf67beef359fCVE reference, Linux
- https://git.kernel.org/stable/c/ffb8c27b0539dd90262d1021488e7817fae57c42CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.