NVD / CVE Program· CNA Linux

CVE-2026-53183: mptcp: allow subflow rcv wnd to shrink

Noroxi assessment

Priority: Monitor (action score 30/100)

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: 0.49% (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 653245266913f03fcf21cbca68eed5c197a33e52, aa3861f40ac32706d9e97bfac76984613e278788, b1fd13074f22105deec45aa02283e322733e0c2d; azl3 kernel 6.6.141.1-1 on Azure Linux 3.0 6.6.143.1-1.

Low priority for now. Upgrade to Linux Linux 653245266913f03fcf21cbca68eed5c197a33e52, aa3861f40ac32706d9e97bfac76984613e278788, b1fd13074f22105deec45aa02283e322733e0c2d; azl3 kernel 6.6.141.1-1 on Azure Linux 3.0 6.6.143.1-1 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: allow subflow rcv wnd to shrink In MPTCP connection, the `window` field in the TCP header refers to the MPTCP-level rcv_nxt and it's right edge should not move backward. Such constraint is enforced at DSS option generation time. At the same time, the TCP stack ensures independently that the TCP-level rcv wnd right's edge does not move backward. That in turn causes artificial inflating of the MPTCP rcv window when the incoming data is acked at the TCP level and is OoO in the MPTCP sequence space (or lands in the backlog). As a consequence, the incoming traffic can exceed the receiver rcvbuf size even when the sender is not misbehaving. Prevent such scenario forcibly allowing the TCP subflow to shrink the TCP-level rcv wnd regardless of the current netns setting.

HighCVSS 7.5 · v3.1—No exploit Fix available

BDU:2026-14025

Published: Jun 25, 2026
Updated: Oct 19, 2026
EPSS: 0.4% · 42th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Linux: 7.5; 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.

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.

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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 kernel5.19 and later · before 6.1.176
linux linux kernel6.2 and later · before 6.6.143
linux linux kernel6.7 and later · before 6.12.94
linux linux kernel6.13 and later · before 6.18.36
linux linux kernel6.19 and later · before 7.0.13
linux linux kernel7.1

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
- 5.19affected
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before bf364b0f10b27679140699821f88af7f01e2a6e3affected · git
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before b1fd13074f22105deec45aa02283e322733e0c2daffected · git
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before aa3861f40ac32706d9e97bfac76984613e278788affected · git
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before 653245266913f03fcf21cbca68eed5c197a33e52affected · git
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before c297a4e65c50a2b807d9309b22615080faffa8f3affected · git
- f3589be0c420a3137e5902d15705ced6a36f3f43 and later · before da23be77e1292cd611e736c3aa17da633d7ddce7affected · git
- before 5.19not affected · semver
- 6.1.176 and later · up to and including 6.1.*not affected · semver
- 6.6.143 and later · up to and including 6.6.*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
Debian:12	linux	before 6.1.176-1	6.1.176-1
Debian:13	linux	before 6.12.94-1	6.12.94-1
Debian:14	linux	before 7.0.13-1	7.0.13-1

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-2026-53181Jun 25, 2026 · vsock/vmci: fix sk_ack_backlog leak on failed handshake
22Monitor
← EarlierCVE-2026-53182Jun 25, 2026 · wifi: nl80211: reject oversized EMA RNR lists
31Monitor
Later →CVE-2026-53184Jun 25, 2026 · udp: clear skb->dev before running a sockmap verdict
30Monitor

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	653245266913f03fcf21cbca68eed5c197a33e52	Vendor (CNA)
Linux Linux	aa3861f40ac32706d9e97bfac76984613e278788	Vendor (CNA)
Linux Linux	b1fd13074f22105deec45aa02283e322733e0c2d	Vendor (CNA)
Linux Linux	bf364b0f10b27679140699821f88af7f01e2a6e3	Vendor (CNA)
Linux Linux	c297a4e65c50a2b807d9309b22615080faffa8f3	Vendor (CNA)
Linux Linux	da23be77e1292cd611e736c3aa17da633d7ddce7	Vendor (CNA)
azl3 kernel 6.6.141.1-1 on Azure Linux 3.0	6.6.143.1-1 · CBL-Mariner Releases	Microsoft (MSRC)
debian:linux	6.1.176-1 · Debian:12	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.

CVE-2026-4627322 days apartibmveth: Disable GSO for packets with small MSS
34Monitor
CVE-2025-38501313 days apartksmbd: limit repeated connections from clients with the same IP
31Monitor
CVE-2026-6417524 days apartwifi: iwlwifi: mld: stop TX during firmware restart
30Monitor
CVE-2026-4585929 days apartnetfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation
30Monitor
CVE-2026-4586029 days apartnetfilter: nf_conncount: increase the connection clean up limit to 64
30Monitor
CVE-2026-23086141 days apartvsock/virtio: cap TX credit to local buffer size
22Monitor

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: none
Integrity: none
Availability: high · the service can be disrupted

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

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

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

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

SSVC exploitation— → noneOct 16, 2026, 5:07 PM UTC
Fix✗ → ✓Sep 28, 2026, 10:08 PM UTC

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

References

git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52

Show all references (6 more)

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

All records