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NVD / CVE Program· CNA Linux

CVE-2025-71126: mptcp: avoid deadlock on fallback while reinjecting

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.26% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 0107442e82c0f8d6010e07e6030741c59c520d6e, 0ca9fb4335e726dab4f23b3bfe87271d8f005f41, 252892d5a6a2f163ce18f32716e46fa4da7d4e79.
  • Severity is disputed: the assigning authority (CNA) scores it 7.5, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 0107442e82c0f8d6010e07e6030741c59c520d6e, 0ca9fb4335e726dab4f23b3bfe87271d8f005f41, 252892d5a6a2f163ce18f32716e46fa4da7d4e79 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: mptcp: avoid deadlock on fallback while reinjecting Jakub reported an MPTCP deadlock at fallback time: WARNING: possible recursive locking detected 6.18.0-rc7-virtme #1 Not tainted -------------------------------------------- mptcp_connect/20858 is trying to acquire lock: ff1100001da18b60 (&msk->fallback_lock){+.-.}-{3:3}, at: __mptcp_try_fallback+0xd8/0x280 but task is already holding lock: ff1100001da18b60 (&msk->fallback_lock){+.-.}-{3:3}, at: __mptcp_retrans+0x352/0xaa0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&msk->fallback_lock); lock(&msk->fallback_lock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by mptcp_connect/20858: #0: ff1100001da18290 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_sendmsg+0x114/0x1bc0 #1: ff1100001db40fd0 (k-sk_lock-AF_INET#2){+.+.}-{0:0}, at: __mptcp_retrans+0x2cb/0xaa0 #2: ff1100001da18b60 (&msk->fallback_lock){+.-.}-{3:3}, at: __mptcp_retrans+0x352/0xaa0 stack backtrace: CPU: 0 UID: 0 PID: 20858 Comm: mptcp_connect Not tainted 6.18.0-rc7-virtme #1 PREEMPT(full) Hardware name: Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dump_stack_lvl+0x6f/0xa0 print_deadlock_bug.cold+0xc0/0xcd validate_chain+0x2ff/0x5f0 __lock_acquire+0x34c/0x740 lock_acquire.part.0+0xbc/0x260 _raw_spin_lock_bh+0x38/0x50 __mptcp_try_fallback+0xd8/0x280 mptcp_sendmsg_frag+0x16c2/0x3050 __mptcp_retrans+0x421/0xaa0 mptcp_release_cb+0x5aa/0xa70 release_sock+0xab/0x1d0 mptcp_sendmsg+0xd5b/0x1bc0 sock_write_iter+0x281/0x4d0 new_sync_write+0x3c5/0x6f0 vfs_write+0x65e/0xbb0 ksys_write+0x17e/0x200 do_syscall_64+0xbb/0xfd0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7fa5627cbc5e Code: 4d 89 d8 e8 14 bd 00 00 4c 8b 5d f8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 11 c9 c3 0f 1f 80 00 00 00 00 48 8b 45 10 0f 05 <c9> c3 83 e2 39 83 fa 08 75 e7 e8 13 ff ff ff 0f 1f 00 f3 0f 1e fa RSP: 002b:00007fff1fe14700 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007fa5627cbc5e RDX: 0000000000001f9c RSI: 00007fff1fe16984 RDI: 0000000000000005 RBP: 00007fff1fe14710 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff1fe16920 R13: 0000000000002000 R14: 0000000000001f9c R15: 0000000000001f9c The packet scheduler could attempt a reinjection after receiving an MP_FAIL and before the infinite map has been transmitted, causing a deadlock since MPTCP needs to do the reinjection atomically from WRT fallback. Address the issue explicitly avoiding the reinjection in the critical scenario. Note that this is the only fallback critical section that could potentially send packets and hit the double-lock.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Jan 14, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 18th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · Linux
7.5
2.0 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-71126

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel6.1.149 and later · before 6.1.160
  • linux linux kernel6.6.101 and later · before 6.6.120
  • linux linux kernel6.12.40 and later · before 6.12.64
  • linux linux kernel6.15.8 and later · before 6.16
  • linux linux kernel6.16.1 and later · before 6.18.3
  • linux linux kernel6.16
  • linux linux kernel6.19

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 1d82a8fe6ee4afdc92f4e8808c9dad2a6095bbc5, 6.16affected
    • 5586518bec27666c747cd52aabb62d485686d0bf and later · before 0107442e82c0f8d6010e07e6030741c59c520d6eaffected · git
    • 75a4c9ab8a7af0d76b31ccd1188ed178c38b35d2 and later · before 252892d5a6a2f163ce18f32716e46fa4da7d4e79affected · git
    • 54999dea879fecb761225e28f274b40662918c30 and later · before 0ca9fb4335e726dab4f23b3bfe87271d8f005f41affected · git
    • f8a1d9b18c5efc76784f5a326e905f641f839894 and later · before 50f47c02be419bf0a3ae94c118addf67beef359faffected · git
    • f8a1d9b18c5efc76784f5a326e905f641f839894 and later · before ffb8c27b0539dd90262d1021488e7817fae57c42affected · git
    • 6.1.149 and later · before 6.1.160affected · semver
    • 6.6.101 and later · before 6.6.120affected · semver
    • 6.12.40 and later · before 6.12.64affected · semver
    • 6.15.8 and later · before 6.16affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.162-16.1.162-1
Debian:13linuxbefore 6.12.69-16.12.69-1
Debian:14linuxbefore 6.18.3-16.18.3-1
SUSE:Linux Micro 6.1kernel-defaultbefore 6.4.0-40.16.4.0-40.1
SUSE:Linux Micro 6.1kernel-default-basebefore 6.4.0-40.1.21.176.4.0-40.1.21.17
SUSE:Linux Micro 6.1kernel-kvmsmallbefore 6.4.0-40.16.4.0-40.1
SUSE:Linux Micro 6.1kernel-sourcebefore 6.4.0-40.16.4.0-40.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-71123Jan 14, 2026 · ext4: fix string copying in parse_apply_sb_mount_options()
    31Monitor
  • ← EarlierCVE-2025-71125Jan 14, 2026 · tracing: Do not register unsupported perf events
    22Monitor
  • Later →CVE-2025-71127Jan 14, 2026 · wifi: mac80211: Discard Beacon frames to non-broadcast address
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0107442e82c0f8d6010e07e6030741c59c520d6eVendor (CNA)
Linux Linux0ca9fb4335e726dab4f23b3bfe87271d8f005f41Vendor (CNA)
Linux Linux252892d5a6a2f163ce18f32716e46fa4da7d4e79Vendor (CNA)
Linux Linux50f47c02be419bf0a3ae94c118addf67beef359fVendor (CNA)
Linux Linux6.1.160Vendor (CNA)
Linux Linux6.12.64Vendor (CNA)
Linux Linux6.16Vendor (CNA)
Linux Linux6.6.120Vendor (CNA)
Linux Linuxffb8c27b0539dd90262d1021488e7817fae57c42Vendor (CNA)
debian:linux6.1.162-1 · Debian:12Package registry (OSV)
suse:kernel-default6.4.0-40.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-default-base6.4.0-40.1.21.17 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-kvmsmall6.4.0-40.1 · SUSE:Linux Micro 6.1Package registry (OSV)
suse:kernel-source6.4.0-40.1 · SUSE:Linux Micro 6.1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-667 · Improper Locking

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records