CVE-2026-64538: Linux kernel · ipv6: Fix null-ptr-deref in fib6_nh_mtu_change(). fib6_nh_mtu_change() re-fetches idev
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.15.0-1117.124~20.04.1 : 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 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +55
Exploitation evidence
Disclosed: evidence found.
CVE published 27 Jul 2026
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 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther 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
A patch is available and should be applied to affected Linux kernel versions to resolve this null pointer dereference vulnerability. The vendor advisory confirms that the issue has been fixed. Users should update their Linux kernel to the fixed versions as provided by their distribution or vendor.
Description
A null pointer dereference vulnerability in the Linux kernel's IPv6 implementation (fib6_nh_mtu_change function) has been fixed. The issue occurs because the function dereferences a pointer without checking for NULL, which can lead to a kernel oops (crash). This flaw affects specific Linux kernel versions and could cause denial of service due to system crashes. A patch is available to address this vulnerability.
References
- ubuntu.com/security/CVE-2026-64538 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-64538 (opens in a new tab)
- git.kernel.org/linus/46c3b8191aad3d032776bf3bebf03efdf5f4b905 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-64538 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f (opens in a new tab)
- git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9 (opens in a new tab)
- git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905 (opens in a new tab)
- git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967 (opens in a new tab)
- git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5 (opens in a new tab)
- git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33 (opens in a new tab)
- git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a (opens in a new tab)
- git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b (opens in a new tab)
- ubuntu.com/security/notices/USN-8876-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8889-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8917-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8918-1 (opens in a new tab)