CVE-2025-40046Network attack vector

Receive-limit bypass via fragment double accounting

Published Oct 28, 2025 · Updated Oct 28, 2025

Receive-limit bypass in Linux kernel 6.15 through 6.17.2 allows remote attackers to overrun an io_uring zero-copy receive length. io_zcrx_recv_skb() counts frag-list buffers, then counts them again during recursive processing, causing desc->count to underflow. A service must register a zero-copy receive queue with CAP_NET_ADMIN and process fragmented input; extra bytes can cross the requested boundary and break the receive request.

CVSS severity8.6
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Receive-limit bypass in Linux kernel 6.15 through 6.17.2 allows remote attackers to overrun an io_uring zero-copy receive length. io_zcrx_recv_skb() counts frag-list buffers, then counts them again during recursive processing, causing desc->count to underflow. A service must register a zero-copy receive queue with CAP_NET_ADMIN and process fragmented input; extra bytes can cross the requested boundary and break the receive request.

The record

CVE
CVE-2025-40046
Published
Oct 28, 2025
Updated
Oct 28, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 28, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.15
  2. Affected versionversion=6699ec9a23f85f1764183430209c741847c45f12 <09cfd3c52ea76f43b3cb15e570aeddf633d65e80
  3. Affected versionversion=6699ec9a23f85f1764183430209c741847c45f12 <8bcc9eaf1b19f1a7029cba19f6bd4122b40f6c4f

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.15; version=6699ec9a23f85f1764183430209c741847c45f12 <09cfd3c52ea76f43b3cb15e570aeddf633d65e80; version=6699ec9a23f85f1764183430209c741847c45f12 <8bcc9eaf1b19f1a7029cba19f6bd4122b40f6c4f

Published CVSS scores

8.6Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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