NVD / CVE Program· CNA Linux

CVE-2026-31669: mptcp: fix slab-use-after-free in __inet_lookup_established

CriticalCVSS 9.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 39/100)

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: 0.47% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. 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 15fa9ead4d5e6b6b9c794e84144146c917f2cb62, 3fd6547f5b8ac99687be6d937a0321efda760597, 9b55b253907e7431210483519c5ad711a37dafa1; azl3 kernel 6.6.134.1-2 on Azure Linux 3.0 6.6.137.1-1.

Low priority for now. Upgrade to Linux Linux 15fa9ead4d5e6b6b9c794e84144146c917f2cb62, 3fd6547f5b8ac99687be6d937a0321efda760597, 9b55b253907e7431210483519c5ad711a37dafa1; azl3 kernel 6.6.134.1-2 on Azure Linux 3.0 6.6.137.1-1 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: fix slab-use-after-free in __inet_lookup_established The ehash table lookups are lockless and rely on SLAB_TYPESAFE_BY_RCU to guarantee socket memory stability during RCU read-side critical sections. Both tcp_prot and tcpv6_prot have their slab caches created with this flag via proto_register(). However, MPTCP's mptcp_subflow_init() copies tcpv6_prot into tcpv6_prot_override during inet_init() (fs_initcall, level 5), before inet6_init() (module_init/device_initcall, level 6) has called proto_register(&tcpv6_prot). At that point, tcpv6_prot.slab is still NULL, so tcpv6_prot_override.slab remains NULL permanently. This causes MPTCP v6 subflow child sockets to be allocated via kmalloc (falling into kmalloc-4k) instead of the TCPv6 slab cache. The kmalloc-4k cache lacks SLAB_TYPESAFE_BY_RCU, so when these sockets are freed without SOCK_RCU_FREE (which is cleared for child sockets by design), the memory can be immediately reused. Concurrent ehash lookups under rcu_read_lock can then access freed memory, triggering a slab-use-after-free in __inet_lookup_established. Fix this by splitting the IPv6-specific initialization out of mptcp_subflow_init() into a new mptcp_subflow_v6_init(), called from mptcp_proto_v6_init() before protocol registration. This ensures tcpv6_prot_override.slab correctly inherits the SLAB_TYPESAFE_BY_RCU slab cache.

Published: Apr 24, 2026
Updated: Nov 11, 2026
EPSS: 0.4% · 41th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Linux: 9.8; NVD has not scored this yet; the score shown is the CNA’s.

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

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No public exploit code on record
A fix has been released

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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.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

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

linux linux kernel5.12.1 and later · before 5.15.203
linux linux kernel5.16 and later · before 6.1.169
linux linux kernel6.2 and later · before 6.6.135
linux linux kernel6.7 and later · before 6.12.82
linux linux kernel6.13 and later · before 6.18.23
linux linux kernel6.19 and later · before 6.19.13
linux linux kernel5.12
linux linux kernel7.0

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
- 5.12affected
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47affected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before fb1f54b7d16f393b8b65d328410f78b4beea8fccaffected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before 3fd6547f5b8ac99687be6d937a0321efda760597affected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before eb9c6aeb512f877cf397deb1e4526f646c70e4a7affected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before 15fa9ead4d5e6b6b9c794e84144146c917f2cb62affected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before b313e9037d98c13938740e5ebda7852929366dffaffected · git
- b19bc2945b40b9fd38e835700907ffe8534ef0de and later · before 9b55b253907e7431210483519c5ad711a37dafa1affected · git
- before 5.12not affected · semver
- 5.15.203 and later · up to and including 5.15.*not affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
AlmaLinux:10	kernel	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-devel	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-devel-matched	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-modules	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-modules-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-debug-modules-extra	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-devel	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-devel-matched	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-modules	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-modules-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-64k-modules-extra	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-abi-stablelists	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-cross-headers	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug-devel	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug-devel-matched	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug-modules	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2
AlmaLinux:10	kernel-debug-modules-core	before 6.12.0-211.26.1.el10_2	6.12.0-211.26.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

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Published before and after this one in the same product

← EarlierCVE-2026-31667Apr 24, 2026 · Input: uinput - fix circular locking dependency with ff-core
31Monitor
← EarlierCVE-2026-31668Apr 24, 2026 · seg6: separate dst_cache for input and output paths in seg6 lwtunnel
39Monitor
Later →CVE-2026-31670Apr 24, 2026 · net: rfkill: prevent unlimited numbers of rfkill events from being created
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 / package	Fixed version	Source
Linux Linux	15fa9ead4d5e6b6b9c794e84144146c917f2cb62	Vendor (CNA)
Linux Linux	3fd6547f5b8ac99687be6d937a0321efda760597	Vendor (CNA)
Linux Linux	9b55b253907e7431210483519c5ad711a37dafa1	Vendor (CNA)
Linux Linux	b313e9037d98c13938740e5ebda7852929366dff	Vendor (CNA)
Linux Linux	eb9c6aeb512f877cf397deb1e4526f646c70e4a7	Vendor (CNA)
Linux Linux	f6e1f25fa5e733570f6d6fe37a4dfed2a0deba47	Vendor (CNA)
Linux Linux	fb1f54b7d16f393b8b65d328410f78b4beea8fcc	Vendor (CNA)
azl3 kernel 6.6.134.1-2 on Azure Linux 3.0	6.6.137.1-1 · CBL-Mariner Releases	Microsoft (MSRC)
almalinux:bpftool	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-abi-stablelists	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-core	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-cross-headers	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-core	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-devel	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-modules	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-modules-extra	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-devel	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-doc	4.18.0-553.134.1.el8_10 · AlmaLinux:8	Package registry (OSV)
debian:linux	6.1.170-1 · Debian:12	Package registry (OSV)
red hat:bpftool	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:bpftool-debuginfo	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-abi-stablelists	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-core	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-debug	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-debug-core	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-debug-debuginfo	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package registry (OSV)
red hat:kernel-debug-devel	0:4.18.0-553.134.1.el8_10 · Red Hat:enterprise_linux:8::baseos	Package 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

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

SSVC exploitation— → noneOct 16, 2026, 5:07 PM UTC
Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

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

References

git.kernel.org/stable/c/15fa9ead4d5e6b6b9c794e84144146c917f2cb62

Show all references (9 more)

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

All records