High

CVE-2025-40173 — net/ip6_tunnel: Prevent perpetual tunnel growth

In the Linux kernel, the following vulnerability has been resolved: net/ip6_tunnel: Prevent perpetual tunnel growth Similarly to ipv4 tunnel, ipv6 version updates dev->needed_headroom, too. While ipv4 tunnel headroom adjustment growth was limited in commit 5ae1e9922bbd ("net: ip_tunnel: prevent perpetual headroom growth"), ipv6 tunnel yet increases the headroom without any ceiling. Reflect ipv4 tunnel headroom adjustment limit on ipv6 version. Credits to Francesco Ruggeri, who was originally debugging this issue and wrote local Arista-specific patch and a reproducer.

Published Nov 12, 2025 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.15%

ahead of 4% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

7.8

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 566f8d5c8a443f2dd69c5460fdec43ed1c870c65≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 11f6066af3bfb8149aa16c42c0b0c5ea5b199a94≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 402b6985e872b4cf394bbbf33b503947a326a6cb≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 10fe967efe73c610e526ff7460581610633dee9c≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 48294a67863c9cfa367abb66bbf0ef6548ae124f≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < eeb4345488672584db4f8c20a1ae13a212ce31c4≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < b6eb25d870f1a8ae571fd3da2244b71df547824b≥ 8eb30be0352d09165e94a41fef1c7b994dca0714 and < 21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16 and 1 more version 4.7	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.8	CVSS 3.1	High	1.8	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
7.8	CVSS 3.1	High	—	—	GitHub, Inc. via GitHub Security Advisories
7.8	CVSS 3.1	High	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.15%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 7.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
2025
CVE published
Nov 12, 2025 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 15, 2026 – Oct 15, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

10 on the record

git.kernel.org/stable/c/11f6066af3bfb8149aa16c42c0b0c5ea5b199a94
NIST National Vulnerability Database
github.com/advisories/GHSA-hr9g-hq4q-3hfj
GitHub Security Advisories
git.kernel.org/stable/c/402b6985e872b4cf394bbbf33b503947a326a6cb
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2025-40173
GitHub Security Advisories
git.kernel.org/stable/c/21f4d45eba0b2dcae5dbc9e5e0ad08735c993f16
NIST National Vulnerability Database
git.kernel.org/stable/c/566f8d5c8a443f2dd69c5460fdec43ed1c870c65
NIST National Vulnerability Database
git.kernel.org/stable/c/10fe967efe73c610e526ff7460581610633dee9c
NIST National Vulnerability Database
git.kernel.org/stable/c/b6eb25d870f1a8ae571fd3da2244b71df547824b
NIST National Vulnerability Database
git.kernel.org/stable/c/48294a67863c9cfa367abb66bbf0ef6548ae124f
NIST National Vulnerability Database
git.kernel.org/stable/c/eeb4345488672584db4f8c20a1ae13a212ce31c4
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 10h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 10h
Unknown CVE-2026-98431 RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 1d
Unknown CVE-2026-98430 RDMA/efa: Keep admin queues alive while IRQ is registered 1d
Unknown CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 1d
Unknown CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-40173 is "net/ip6_tunnel: Prevent perpetual tunnel growth", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. EPSS 0.15% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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