CVE-2025-40363 json
net: ipv6: fix field-spanning memcpy warning in AH output
published 2025-12-16 10 mo ago modified 2026-10-14 26 d ago also EUVD-2025-203730
- cvss
- —
- not scored
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 11%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- Linux Linux 5.4.302, 5.10.247, 5.15.197, 6.1.159, 6.6.117, 6.12.58, 6.17.8, 6.18
- linux Debian 12 6.1.159-1
- linux Debian 13 6.12.63-1
- linux Debian 14 6.17.8-1
debian advisories DEBIAN-CVE-2025-40363
- linux Ubuntu 22.04 LTS 5.15.0-173.183
- linux Ubuntu 24.04 LTS 6.8.0-106.106
- linux Ubuntu 25.10 6.17.0-14.14
- linux-aws Ubuntu 22.04 LTS 5.15.0-1103.110
- linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
- linux-aws Ubuntu 25.10 6.17.0-1007.7
- linux-gcp Ubuntu 22.04 LTS 5.15.0-1103.112
- linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
ubuntu advisories UBUNTU-CVE-2025-40363
Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
- kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-40.1
- kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-40.1
- kernel-rt Linux Micro 6.2 6.12.0-160000.26.1
- kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1
- kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1
- kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.26.1
- kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1.160000.2.7
- kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1
suse advisories SUSE-SU-2026:20845-1SUSE-SU-2026:20876-1SUSE-SU-2026:20555-1SUSE-SU-2026:20599-1SUSE-SU-2026:20615-1SUSE-SU-2026:20570-1
- kernel-rt openSUSE Leap 16.0 6.12.0-160000.26.1
- dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-64kb openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-syms openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-azure openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-source openSUSE Leap 16.0 6.12.0-160000.26.1
- kernel-default openSUSE Leap 16.0 6.12.0-160000.26.1
opensuse advisories openSUSE-SU-2026:20287-1
- git.kernel.org/stable/c/2da805a61ef5272a2773775ce14c3650adb84248 commit
- git.kernel.org/stable/c/9bf27de51bd6db5ff827780ec0eba55de230ba45 commit
- git.kernel.org/stable/c/0bf756ae1e69fec5e6332c37830488315d6d771b commit
- git.kernel.org/stable/c/75b16b2755e12999ad850756ddfb88ad4bfc7186 commit
- git.kernel.org/stable/c/f28dde240160f3c48a50d641d210ed6a3b9596ed commit
- git.kernel.org/stable/c/c14cf41094136691c92ef756872570645d61f4a1 commit
- git.kernel.org/stable/c/b056f971bd72b373b7ae2025a8f3bd18f69653d3 commit
- git.kernel.org/stable/c/2327a3d6f65ce2fe2634546dde4a25ef52296fec commit
Vendor advisories
What the vendors themselves say about their products: affected, fixed or not affected, and what to do.
red hat product security vex CVE-2025-40363 updated cvss 5.5
kernel: net: ipv6: fix field-spanning memcpy warning in AH output
-
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 moreaffected: no fix planned “Out of support scope”
-
Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernelaffected: no fix available “Fix deferred”
Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).
Affected products
- Linux Linux
Classification
- Technology feeds
References
- git.kernel.org /stable/c/2da805a61ef5272a2773775ce14c3650adb84248
- git.kernel.org /stable/c/9bf27de51bd6db5ff827780ec0eba55de230ba45
- git.kernel.org /stable/c/0bf756ae1e69fec5e6332c37830488315d6d771b
- git.kernel.org /stable/c/75b16b2755e12999ad850756ddfb88ad4bfc7186
- git.kernel.org /stable/c/f28dde240160f3c48a50d641d210ed6a3b9596ed
- git.kernel.org /stable/c/c14cf41094136691c92ef756872570645d61f4a1
- git.kernel.org /stable/c/b056f971bd72b373b7ae2025a8f3bd18f69653d3
- git.kernel.org /stable/c/2327a3d6f65ce2fe2634546dde4a25ef52296fec
Sources
- CVE List CVE-2025-40363
- NVD CVE-2025-40363
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