Linux: Use After Free
CVE-2026-43376 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 302fef75512b2c8329a3f5efab1ae7ba2562387a, 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c, 1d6abf145615dbfe267ce3b0a271f95e3780e18e 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 0.44% 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 302fef75512b2c8329a3f5efab1ae7ba2562387a or 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c or 1d6abf145615dbfe267ce3b0a271f95e3780e18e or ce8507ee82c888126d8e7565e27c016308d24cde, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.130 or 6.12.78 or 6.15 or 6.18.19, 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 | 296cb5457cc6f4a754c4ae29855f8a253d52bcc6 up to, but not including, 302fef75512b2c8329a3f5efab1ae7ba2562387a; d54ab1520d43e95f9b2e22d7a05fc9614192e5a5 up to, but not including, 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c; 18b4fac5ef17f77fed9417d22210ceafd6525fc7 up to, but not including, 1d6abf145615dbfe267ce3b0a271f95e3780e18e; 18b4fac5ef17f77fed9417d22210ceafd6525fc7 up to, but not including, ce8507ee82c888126d8e7565e27c016308d24cde; 18b4fac5ef17f77fed9417d22210ceafd6525fc7 up to, but not including, 1dfd062caa165ec9d7ee0823087930f3ab8a6294; d73686367ad68534257cd88a36ca3c52cb8b81d8; 6.6.88 up to, but not including, 6.6.130; 6.12.25 up to, but not including, 6.12.78; and 2 more ranges | 302fef75512b2c8329a3f5efab1ae7ba2562387a, 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c, 1d6abf145615dbfe267ce3b0a271f95e3780e18e, ce8507ee82c888126d8e7565e27c016308d24cde, 1dfd062caa165ec9d7ee0823087930f3ab8a6294, 6.6.130 |
| Linux | Linux Kernel | 6.6.88 up to, but not including, 6.6.130; 6.12.25 up to, but not including, 6.12.78; 6.14.4 up to, but not including, 6.15; 6.15.1 up to, but not including, 6.18.19; 6.19 up to, but not including, 6.19.9; 6.15; 7.0 | 6.6.130, 6.12.78, 6.15, 6.18.19, 6.19.9 |
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: fix use-after-free by using call_rcu() for oplock_info ksmbd currently frees oplock_info immediately using kfree(), even though it is accessed under RCU read-side critical sections in places like opinfo_get() and proc_show_files(). Since there is no RCU grace period delay between nullifying the pointer and freeing the memory, a reader can still access oplock_info structure after it has been freed. This can leads to a use-after-free especially in opinfo_get() where atomic_inc_not_zero() is called on already freed memory. Fix this by switching to deferred freeing using call_rcu().
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/08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c
- git.kernel.org/stable/c/1d6abf145615dbfe267ce3b0a271f95e3780e18e
- git.kernel.org/stable/c/1dfd062caa165ec9d7ee0823087930f3ab8a6294
- git.kernel.org/stable/c/302fef75512b2c8329a3f5efab1ae7ba2562387a
- git.kernel.org/stable/c/ce8507ee82c888126d8e7565e27c016308d24cde
Recent Use After Free vulnerabilities
- 7.3 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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