CVE-2025-40255: Linux kernel · net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 6.17.0-1009.9~24.04.2 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 14:05 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.17.0-1009.9~24.04.2, 6.17.0-1010.10~24.04.1, 6.17.0-1009.9~24.04.3 +11
Exploitation evidence
Disclosed: evidence found.
CVE published 4 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.
Patches and advisories
- ubuntu.com/security/notices/USN-8094-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8152-1 (opens in a new tab)
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.
Description
In the Linux kernel, the following vulnerability has been resolved: net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower() The ethtool tsconfig Netlink path can trigger a null pointer dereference. A call chain such as: tsconfig_prepare_data() -> dev_get_hwtstamp_phylib() -> vlan_hwtstamp_get() -> generic_hwtstamp_get_lower() -> generic_hwtstamp_ioctl_lower() results in generic_hwtstamp_ioctl_lower() being called with kernel_cfg->ifr as NULL. The generic_hwtstamp_ioctl_lower() function does not expect a NULL ifr and dereferences it, leading to a system crash. Fix this by adding a NULL check for kernel_cfg->ifr in generic_hwtstamp_ioctl_lower(). If ifr is NULL, return -EINVAL.
References
- ubuntu.com/security/CVE-2025-40255 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-40255 (opens in a new tab)
- git.kernel.org/linus/f796a8dec9beafcc0f6f0d3478ed685a15c5e062 (opens in a new tab)
- git.kernel.org/stable/c/8817f816ae41908e9625c0770c4af0dcdcc01238 (opens in a new tab)
- git.kernel.org/stable/c/f796a8dec9beafcc0f6f0d3478ed685a15c5e062 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8094-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-8152-1 (opens in a new tab)