CVE-2025-40363: Linux kernel · net: ipv6: fix field-spanning memcpy warning in AH output
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.15.0-1103.110~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 17:16 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1103.110~20.04.1, 5.15.0-1110.119~20.04.1, 5.15.0-1114.123~20.04.1 +70
Exploitation evidence
Disclosed: evidence found.
CVE published 16 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official fix is available and has been released in updated Linux kernel versions. Users should apply the security updates provided by their Linux distribution, such as those from Ubuntu Security Notices (e.g., USN-8029-1). No additional mitigation actions are required beyond applying the official patches.
Description
A vulnerability in the Linux kernel's IPv6 networking code related to field-spanning memcpy warnings in the AH output functions has been resolved. The issue involved improper copying of IPv6 addresses and extension headers, triggering fortify-string warnings about writes beyond the 16-byte address fields. The warnings were false positives due to intentional memory layout, but the code was fixed to copy addresses and extension headers separately and to reduce code duplication. This vulnerability affects multiple Linux kernel versions prior to specific patched releases and has been officially fixed.
References
- ubuntu.com/security/CVE-2025-40363 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-40363 (opens in a new tab)
- git.kernel.org/linus/2327a3d6f65ce2fe2634546dde4a25ef52296fec (opens in a new tab)
- git.kernel.org/stable/c/0bf756ae1e69fec5e6332c37830488315d6d771b (opens in a new tab)
- git.kernel.org/stable/c/2327a3d6f65ce2fe2634546dde4a25ef52296fec (opens in a new tab)
- git.kernel.org/stable/c/2da805a61ef5272a2773775ce14c3650adb84248 (opens in a new tab)
- git.kernel.org/stable/c/75b16b2755e12999ad850756ddfb88ad4bfc7186 (opens in a new tab)
- git.kernel.org/stable/c/9bf27de51bd6db5ff827780ec0eba55de230ba45 (opens in a new tab)
- git.kernel.org/stable/c/b056f971bd72b373b7ae2025a8f3bd18f69653d3 (opens in a new tab)
- git.kernel.org/stable/c/c14cf41094136691c92ef756872570645d61f4a1 (opens in a new tab)
- git.kernel.org/stable/c/f28dde240160f3c48a50d641d210ed6a3b9596ed (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8030-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8048-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8029-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8096-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8100-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8095-2 (opens in a new tab)