Unknown

CVE-2025-40363 — net: ipv6: fix field-spanning memcpy warning in AH output

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix field-spanning memcpy warning in AH output Fix field-spanning memcpy warnings in ah6_output() and ah6_output_done() where extension headers are copied to/from IPv6 address fields, triggering fortify-string warnings about writes beyond the 16-byte address fields. memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16) WARNING: CPU: 0 PID: 8838 at net/ipv6/ah6.c:439 ah6_output+0xe7e/0x14e0 net/ipv6/ah6.c:439 The warnings are false positives as the extension headers are intentionally placed after the IPv6 header in memory. Fix by properly copying addresses and extension headers separately, and introduce helper functions to avoid code duplication.

Published Dec 16, 2025 · Updated Oct 14, 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)+2

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

0.21%

ahead of 11% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

—

Score not published yet.

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

Partial

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	≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 2da805a61ef5272a2773775ce14c3650adb84248≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 9bf27de51bd6db5ff827780ec0eba55de230ba45≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 0bf756ae1e69fec5e6332c37830488315d6d771b≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 75b16b2755e12999ad850756ddfb88ad4bfc7186≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < f28dde240160f3c48a50d641d210ed6a3b9596ed≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < c14cf41094136691c92ef756872570645d61f4a1≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < b056f971bd72b373b7ae2025a8f3bd18f69653d3≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 2327a3d6f65ce2fe2634546dde4a25ef52296fec and 1 more version 2.6.12	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.21%

Detection

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

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 13, 2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
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
Dec 16, 2025 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

10 on the record

git.kernel.org/stable/c/c14cf41094136691c92ef756872570645d61f4a1
NIST National Vulnerability Database
git.kernel.org/stable/c/75b16b2755e12999ad850756ddfb88ad4bfc7186
NIST National Vulnerability Database
github.com/advisories/GHSA-9gfg-vfjm-p94q
GitHub Security Advisories
git.kernel.org/stable/c/9bf27de51bd6db5ff827780ec0eba55de230ba45
NIST National Vulnerability Database
git.kernel.org/stable/c/b056f971bd72b373b7ae2025a8f3bd18f69653d3
NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2025-40363
GitHub Security Advisories
git.kernel.org/stable/c/2da805a61ef5272a2773775ce14c3650adb84248
NIST National Vulnerability Database
git.kernel.org/stable/c/f28dde240160f3c48a50d641d210ed6a3b9596ed
NIST National Vulnerability Database
git.kernel.org/stable/c/2327a3d6f65ce2fe2634546dde4a25ef52296fec
NIST National Vulnerability Database
git.kernel.org/stable/c/0bf756ae1e69fec5e6332c37830488315d6d771b
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 22h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 22h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 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 CVSS score published by NVD, the CNA, CISA or GitHub so far.
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-2025-40363 is "net: ipv6: fix field-spanning memcpy warning in AH output", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.21% 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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