Linux: Use After Free
CVE-2026-31403 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 76740c28050dc6db2f5550f1325b00a11bbb3255, c7f406fb341d6747634b8b1fa5461656e5e56076, d1a19217995df9c7e4118f5a2820c5032fef2945 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 76740c28050dc6db2f5550f1325b00a11bbb3255 or c7f406fb341d6747634b8b1fa5461656e5e56076 or d1a19217995df9c7e4118f5a2820c5032fef2945 or e3d77f935639e6ae4b381c80464c31df998d61f4, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.253 or 6.1.167 or 6.6.130 or 6.12.78, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, 76740c28050dc6db2f5550f1325b00a11bbb3255; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, c7f406fb341d6747634b8b1fa5461656e5e56076; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, d1a19217995df9c7e4118f5a2820c5032fef2945; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, e3d77f935639e6ae4b381c80464c31df998d61f4; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, 6a8d70e2ad6aad2c345a5048edcb8168036f97d6; 96d851c4d28de8cc83fe2bd5c6bc2eb8f253a6c5 up to, but not including, e7fcf179b82d3a3730fd8615da01b087cc654d0b; 3.9 | 76740c28050dc6db2f5550f1325b00a11bbb3255, c7f406fb341d6747634b8b1fa5461656e5e56076, d1a19217995df9c7e4118f5a2820c5032fef2945, e3d77f935639e6ae4b381c80464c31df998d61f4, db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6, 6a8d70e2ad6aad2c345a5048edcb8168036f97d6 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 3.9 up to, but not including, 5.10.253; 5.11 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.20; 6.19 up to, but not including, 6.19.10; 7.0 | 5.10.253, 6.1.167, 6.6.130, 6.12.78, 6.18.20, 6.19.10 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: NFSD: Hold net reference for the lifetime of /proc/fs/nfs/exports fd The /proc/fs/nfs/exports proc entry is created at module init and persists for the module's lifetime. exports_proc_open() captures the caller's current network namespace and stores its svc_export_cache in seq->private, but takes no reference on the namespace. If the namespace is subsequently torn down (e.g. container destruction after the opener does setns() to a different namespace), nfsd_net_exit() calls nfsd_export_shutdown() which frees the cache. Subsequent reads on the still-open fd dereference the freed cache_detail, walking a freed hash table. Hold a reference on the struct net for the lifetime of the open file descriptor. This prevents nfsd_net_exit() from running -- and thus prevents nfsd_export_shutdown() from freeing the cache -- while any exports fd is open. cache_detail already stores its net pointer (cd->net, set by cache_create_net()), so exports_release() can retrieve it without additional per-file storage.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/6a8d70e2ad6aad2c345a5048edcb8168036f97d6
- git.kernel.org/stable/c/76740c28050dc6db2f5550f1325b00a11bbb3255
- git.kernel.org/stable/c/c7f406fb341d6747634b8b1fa5461656e5e56076
- git.kernel.org/stable/c/d1a19217995df9c7e4118f5a2820c5032fef2945
- git.kernel.org/stable/c/db4a9f99b12a7ee1c19d86c83a3b752c7effa6c6
- git.kernel.org/stable/c/e3d77f935639e6ae4b381c80464c31df998d61f4
- git.kernel.org/stable/c/e7fcf179b82d3a3730fd8615da01b087cc654d0b
Other references
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
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- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
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