Linux: Use After Free
CVE-2026-64397 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 1426fd79102539bc0ab5c8fced047ad4313b9908, 2a64dbf9c739ddf7a25a066507597bf89f8f73d2, 64dac2d486ec1eb18dc00968b16a230b6b75ec24 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 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 1426fd79102539bc0ab5c8fced047ad4313b9908 or 2a64dbf9c739ddf7a25a066507597bf89f8f73d2 or 64dac2d486ec1eb18dc00968b16a230b6b75ec24 or a1d5d31cad593ea5e1b637f2f39c9ef6d09d1199, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.178 or 6.6.145 or 6.12.96 or 6.18.39, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 1426fd79102539bc0ab5c8fced047ad4313b9908; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 2a64dbf9c739ddf7a25a066507597bf89f8f73d2; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, 64dac2d486ec1eb18dc00968b16a230b6b75ec24; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, a1d5d31cad593ea5e1b637f2f39c9ef6d09d1199; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, fd22b039a5a05bc1d6818e9dcd1001fb432a829d; e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 up to, but not including, be6d26bf27499977c746abc163659915082348d8; 5.15 | 1426fd79102539bc0ab5c8fced047ad4313b9908, 2a64dbf9c739ddf7a25a066507597bf89f8f73d2, 64dac2d486ec1eb18dc00968b16a230b6b75ec24, a1d5d31cad593ea5e1b637f2f39c9ef6d09d1199, fd22b039a5a05bc1d6818e9dcd1001fb432a829d, be6d26bf27499977c746abc163659915082348d8 |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4 | 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/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: ksmbd: serialize QUERY_DIRECTORY requests per file smb2_query_dir() stores a pointer to its stack-allocated private data in the ksmbd_file readdir_data. Concurrent QUERY_DIRECTORY requests using the same file handle can overwrite this pointer while an iterate_dir() callback is still using it, resulting in a stack use-after-free. Add a per-file mutex and hold it while accessing the shared directory enumeration state. The lock covers scan restart, dot entry state, readdir_data setup and iteration, and response construction. This prevents another request from replacing readdir_data.private before the current request has finished using it and also serializes the shared file position.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1426fd79102539bc0ab5c8fced047ad4313b9908
- git.kernel.org/stable/c/2a64dbf9c739ddf7a25a066507597bf89f8f73d2
- git.kernel.org/stable/c/64dac2d486ec1eb18dc00968b16a230b6b75ec24
- git.kernel.org/stable/c/a1d5d31cad593ea5e1b637f2f39c9ef6d09d1199
- git.kernel.org/stable/c/be6d26bf27499977c746abc163659915082348d8
- git.kernel.org/stable/c/fd22b039a5a05bc1d6818e9dcd1001fb432a829d
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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