CVE-2025-39723Network attack vector

Client crash via bogus unbuffered write count

Published Sep 5, 2025 · Updated Sep 5, 2025

Denial of service in Linux kernel branches from 6.10, before 6.12.44, 6.16.4, or 6.17-rc3, allows remote attackers to crash clients. The netfs collector leaves stream->transferred at LONG_MAX when every unbuffered write fails, then returns that bogus count from write_iter so splice cleanup overruns valid pipe buffers. A client process must perform a splice-based write to a CIFS or 9p mount, after which a malicious or failing server can force an oops, hang, or system panic.

CVSS severity7.8
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kernel branches from 6.10, before 6.12.44, 6.16.4, or 6.17-rc3, allows remote attackers to crash clients. The netfs collector leaves stream->transferred at LONG_MAX when every unbuffered write fails, then returns that bogus count from write_iter so splice cleanup overruns valid pipe buffers. A client process must perform a splice-based write to a CIFS or 9p mount, after which a malicious or failing server can force an oops, hang, or system panic.

The record

CVE
CVE-2025-39723
Published
Sep 5, 2025
Updated
Sep 5, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 5, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 5, 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=288ace2f57c9d06dd2e42bd80d03747d879a4068 <387164a2b97e1f5404c6d0049a7409bac7d2bc5b
  2. Affected versionversion=288ace2f57c9d06dd2e42bd80d03747d879a4068 <a3de58b12ce074ec05b8741fa28d62ccb1070468
  3. Affected versionversion=288ace2f57c9d06dd2e42bd80d03747d879a4068 <f08c80af3c9a9849cd178b4843b7c01d103506a1
  4. Affected versionversion=6.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=288ace2f57c9d06dd2e42bd80d03747d879a4068 <387164a2b97e1f5404c6d0049a7409bac7d2bc5b; version=288ace2f57c9d06dd2e42bd80d03747d879a4068 <a3de58b12ce074ec05b8741fa28d62ccb1070468; version=288ace2f57c9d06dd2e42bd80d03747d879a4068 <f08c80af3c9a9849cd178b4843b7c01d103506a1; version=6.10

Published CVSS scores

7.8CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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