NVD / CVE Program· CNA Linux

CVE-2026-23086: vsock/virtio: cap TX credit to local buffer size

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: 0.17% (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.
Fixed version: Linux Linux 84ef86aa7120449828d1e0ce438c499014839711, 8ee784fdf006cbe8739cfa093f54d326cbf54037, c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 84ef86aa7120449828d1e0ce438c499014839711, 8ee784fdf006cbe8739cfa093f54d326cbf54037, c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes 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: vsock/virtio: cap TX credit to local buffer size The virtio transports derives its TX credit directly from peer_buf_alloc, which is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value. On the host side this means that the amount of data we are willing to queue for a connection is scaled by a guest-chosen buffer size, rather than the host's own vsock configuration. A malicious guest can advertise a large buffer and read slowly, causing the host to allocate a correspondingly large amount of sk_buff memory. The same thing would happen in the guest with a malicious host, since virtio transports share the same code base. Introduce a small helper, virtio_transport_tx_buf_size(), that returns min(peer_buf_alloc, buf_alloc), and use it wherever we consume peer_buf_alloc. This ensures the effective TX window is bounded by both the peer's advertised buffer and our own buf_alloc (already clamped to buffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer cannot force the other to queue more data than allowed by its own vsock settings. On an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with 32 guest vsock connections advertising 2 GiB each and reading slowly drove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only recovered after killing the QEMU process. That said, if QEMU memory is limited with cgroups, the maximum memory used will be limited. With this patch applied: Before: MemFree: ~61.6 GiB Slab: ~142 MiB SUnreclaim: ~117 MiB After 32 high-credit connections: MemFree: ~61.5 GiB Slab: ~178 MiB SUnreclaim: ~152 MiB Only ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest remains responsive. Compatibility with non-virtio transports: - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per socket based on the local vsk->buffer_* values; the remote side cannot enlarge those queues beyond what the local endpoint configured. - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and an MTU bound; there is no peer-controlled credit field comparable to peer_buf_alloc, and the remote endpoint cannot drive in-flight kernel memory above those ring sizes. - The loopback path reuses virtio_transport_common.c, so it naturally follows the same semantics as the virtio transport. This change is limited to virtio_transport_common.c and thus affects virtio-vsock, vhost-vsock, and loopback, bringing them in line with the "remote window intersected with local policy" behaviour that VMCI and Hyper-V already effectively have. [Stefano: small adjustments after changing the previous patch] [Stefano: tweak the commit message]

MediumCVSS 5.5 · v3.1—No exploit Fix available

Denial of service

BDU:2026-11567

Published: Feb 4, 2026
Updated: Oct 19, 2026
EPSS: 0.1% · 6th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 22 / 40 · 5.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.1%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

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

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Noroxi analysis

What does it mean in your environment?

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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 kernel4.8 and later · before 6.1.162
linux linux kernel6.2 and later · before 6.6.122
linux linux kernel6.7 and later · before 6.12.68
linux linux kernel6.13 and later · before 6.18.8
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
- 4.8affected
- 06a8fc78367d070720af960dcecec917d3ae5f3b and later · before fef7110ae5617555c792a2bb4d27878d84583adfaffected · git
- 06a8fc78367d070720af960dcecec917d3ae5f3b and later · before d9d5f222558b42f6277eafaaa6080966faf37676affected · git
- 06a8fc78367d070720af960dcecec917d3ae5f3b and later · before c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ceaffected · git
- 06a8fc78367d070720af960dcecec917d3ae5f3b and later · before 84ef86aa7120449828d1e0ce438c499014839711affected · git
- 06a8fc78367d070720af960dcecec917d3ae5f3b and later · before 8ee784fdf006cbe8739cfa093f54d326cbf54037affected · git
- before 4.8not affected · semver
- 6.1.162 and later · up to and including 6.1.*not affected · semver
- 6.6.122 and later · up to and including 6.6.*not affected · semver
- 6.12.68 and later · up to and including 6.12.*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 6.1.162-1	6.1.162-1
Debian:13	linux	before 6.12.69-1	6.12.69-1
Debian:14	linux	before 6.18.8-1	6.18.8-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

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CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
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Published before and after this one in the same product

← EarlierCVE-2026-23084Feb 4, 2026 · be2net: Fix NULL pointer dereference in be_cmd_get_mac_from_list
22Monitor
← EarlierCVE-2026-23085Feb 4, 2026 · irqchip/gic-v3-its: Avoid truncating memory addresses
22Monitor
Later →CVE-2026-23087Feb 4, 2026 · scsi: xen: scsiback: Fix potential memory leak in scsiback_remove()
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	84ef86aa7120449828d1e0ce438c499014839711	Vendor (CNA)
Linux Linux	8ee784fdf006cbe8739cfa093f54d326cbf54037	Vendor (CNA)
Linux Linux	c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce	Vendor (CNA)
Linux Linux	d9d5f222558b42f6277eafaaa6080966faf37676	Vendor (CNA)
Linux Linux	fef7110ae5617555c792a2bb4d27878d84583adf	Vendor (CNA)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0	Release Notes	Microsoft (MSRC)
debian:linux	6.1.162-1 · 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-2026-46273119 days apartibmveth: Disable GSO for packets with small MSS
34Monitor
CVE-2025-38501172 days apartksmbd: limit repeated connections from clients with the same IP
31Monitor
CVE-2026-45859112 days apartnetfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation
30Monitor
CVE-2026-45860112 days apartnetfilter: nf_conncount: increase the connection clean up limit to 64
30Monitor
CVE-2026-53183141 days apartmptcp: allow subflow rcv wnd to shrink
30Monitor
CVE-2026-64175165 days apartwifi: iwlwifi: mld: stop TX during firmware restart
30Monitor

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-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-primary

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

Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

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

References

git.kernel.org/stable/c/84ef86aa7120449828d1e0ce438c499014839711

Show all references (6 more)

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

All records