CVE-2025-39770

Throughput collapse via unsupported IPv6 checksum offload

Published Sep 11, 2025 · Updated Sep 11, 2025

Improper IPv6 GSO handling in the Linux kernel allows local users to collapse network throughput through crafted tunnel traffic. The gso_features_check path fails to mask NETIF_F_IPV6_CSUM when IPv6 extension headers are present, so it requests checksum work that the egress device does not support. Reachability requires local access and an egress device advertising only NETIF_F_IPV6_CSUM; the resulting warning and throughput collapse affect availability.

CVSS severity5.5
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper IPv6 GSO handling in the Linux kernel allows local users to collapse network throughput through crafted tunnel traffic. The gso_features_check path fails to mask NETIF_F_IPV6_CSUM when IPv6 extension headers are present, so it requests checksum work that the egress device does not support. Reachability requires local access and an egress device advertising only NETIF_F_IPV6_CSUM; the resulting warning and throughput collapse affect availability.

The record

CVE
CVE-2025-39770
Published
Sep 11, 2025
Updated
Sep 11, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 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=04c20a9356f283da623903e81e7c6d5df7e4dc3c <041e2f945f82fdbd6fff577b79c33469430297aa
  2. Affected versionversion=04c20a9356f283da623903e81e7c6d5df7e4dc3c <794ddbb7b63b6828c75967b9bcd43b086716e7a1
  3. Affected versionversion=04c20a9356f283da623903e81e7c6d5df7e4dc3c <864e3396976ef41de6cc7bc366276bf4e084fff2
  4. Affected versionversion=477b35d94a21530046fe91589960732fcf2b29ed
  5. Affected versionversion=6.12
  6. Affected versionversion=705350fbd6ed4b5d89ee045fa57a0594a72b17d7
  7. Affected versionversion=9f605135a5c0fe614c2b15197b9ced1e217eca59
  8. Affected versionversion=a27a5c40ee4cbe00294e2c76160de5f2589061ba
  9. Affected versionversion=a84978a9cda68f0afe3f01d476c68db21526baf1 <a0478d7e888028f85fa7785ea838ce0ca09398e2
  10. Affected versionversion=bcefc3cd7f592a70fcbbbfd7ad1fbc69172ea78b
  11. Affected versionversion=c69bc67c1cb211aa390bea6e512bb01b1241fefb <2156d9e9f2e483c8c3906c0ea57ea312c1424235

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=04c20a9356f283da623903e81e7c6d5df7e4dc3c <041e2f945f82fdbd6fff577b79c33469430297aa; version=04c20a9356f283da623903e81e7c6d5df7e4dc3c <794ddbb7b63b6828c75967b9bcd43b086716e7a1; version=04c20a9356f283da623903e81e7c6d5df7e4dc3c <864e3396976ef41de6cc7bc366276bf4e084fff2; version=477b35d94a21530046fe91589960732fcf2b29ed; version=6.12; version=705350fbd6ed4b5d89ee045fa57a0594a72b17d7; version=9f605135a5c0fe614c2b15197b9ced1e217eca59; version=a27a5c40ee4cbe00294e2c76160de5f2589061ba; version=a84978a9cda68f0afe3f01d476c68db21526baf1 <a0478d7e888028f85fa7785ea838ce0ca09398e2; version=bcefc3cd7f592a70fcbbbfd7ad1fbc69172ea78b; version=c69bc67c1cb211aa390bea6e512bb01b1241fefb <2156d9e9f2e483c8c3906c0ea57ea312c1424235

Published CVSS scores

5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
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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