CVE-2026-31403: Linux kernel · Use After Free
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 7.8 High · fixed in e7fcf179b82d3a3730fd8615da01b087cc654d0b : patch Linux kernel soon.
Data as of 26 Oct 2026, 17:30 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in e7fcf179b82d3a3730fd8615da01b087cc654d0b, e3d77f935639e6ae4b381c80464c31df998d61f4, db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6 +4
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 3 Apr 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 |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in
|
AI-suggested
This vulnerability has been fixed in the Linux kernel versions identified by the provided commit hashes. Users and administrators should update to a Linux kernel version that includes these fixes. No additional mitigations are required once the system is patched.
Description
CVE-2026-31403 is a high-severity vulnerability in the Linux kernel's NFSD subsystem. It involves improper handling of network namespace references for the /proc/fs/nfs/exports file descriptor. Without holding a reference to the network namespace, the kernel may free related cache structures prematurely, leading to use-after-free conditions when the file descriptor is accessed after the namespace is torn down. This flaw has been fixed in specific Linux kernel commits.
References
- git.kernel.org/stable/c/76740c28050dc6db2f5550f1325b00a11bbb3255 (opens in a new tab)
- git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076 (opens in a new tab)
- git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945 (opens in a new tab)
- git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4 (opens in a new tab)
- git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6 (opens in a new tab)
- git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6 (opens in a new tab)
- git.kernel.org/stable/c/e7fcf179b82d3a3730fd8615da01b087cc654d0b (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-082556.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)