CVE-2025-40173

Kernel compromise via unbounded tunnel headroom growth

Published Nov 12, 2025 · Updated Aug 5, 2026

Integer overflow in the Linux kernel's IPv6 tunnel path allows local users to compromise or crash the kernel through a routing loop. ip6_tnl_xmit repeatedly increases dev->needed_headroom without a ceiling until a 16-bit header offset wraps, enabling out-of-bounds kernel reads and writes. Local users must create a two-tunnel routing loop and supply packets; a user namespace can provide the required network-administration capability.

CVSS severity7.8
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in the Linux kernel's IPv6 tunnel path allows local users to compromise or crash the kernel through a routing loop. ip6_tnl_xmit repeatedly increases dev->needed_headroom without a ceiling until a 16-bit header offset wraps, enabling out-of-bounds kernel reads and writes. Local users must create a two-tunnel routing loop and supply packets; a user namespace can provide the required network-administration capability.

The record

CVE
CVE-2025-40173
Published
Nov 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068, T1499.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=4.7
  2. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <10fe967efe73c610e526ff7460581610633dee9c
  3. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <11f6066af3bfb8149aa16c42c0b0c5ea5b199a94
  4. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16
  5. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <402b6985e872b4cf394bbbf33b503947a326a6cb
  6. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <48294a67863c9cfa367abb66bbf0ef6548ae124f
  7. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <566f8d5c8a443f2dd69c5460fdec43ed1c870c65
  8. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <b6eb25d870f1a8ae571fd3da2244b71df547824b
  9. Affected versionversion=8eb30be0352d09165e94a41fef1c7b994dca0714 <eeb4345488672584db4f8c20a1ae13a212ce31c4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.7; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <10fe967efe73c610e526ff7460581610633dee9c; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <11f6066af3bfb8149aa16c42c0b0c5ea5b199a94; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <402b6985e872b4cf394bbbf33b503947a326a6cb; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <48294a67863c9cfa367abb66bbf0ef6548ae124f; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <566f8d5c8a443f2dd69c5460fdec43ed1c870c65; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <b6eb25d870f1a8ae571fd3da2244b71df547824b; version=8eb30be0352d09165e94a41fef1c7b994dca0714 <eeb4345488672584db4f8c20a1ae13a212ce31c4

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
4.1OracleCVSS:3.1/AV:L/AC:H/PR:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation
T1499.001OS Exhaustion Flood

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

See the directory against your own environment.

Your stack

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