Linux: Use After Free
CVE-2026-43438 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 cc095cd305fddbe25a968e4a78436ff9476cf0f6, 6eaaa67d6998f6c30c462b140db8c062e07ec473, bf50f3285eda8a0173625fcdb5f183f96e1008cd 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 cc095cd305fddbe25a968e4a78436ff9476cf0f6 or 6eaaa67d6998f6c30c462b140db8c062e07ec473 or bf50f3285eda8a0173625fcdb5f183f96e1008cd or 1336b579f6079fb8520be03624fcd9ba443c930b, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.78 or 6.18.19 or 6.19.9, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 8195136669661fdfe54e9a8923c33b31c92fc1da up to, but not including, cc095cd305fddbe25a968e4a78436ff9476cf0f6; 8195136669661fdfe54e9a8923c33b31c92fc1da up to, but not including, 6eaaa67d6998f6c30c462b140db8c062e07ec473; 8195136669661fdfe54e9a8923c33b31c92fc1da up to, but not including, bf50f3285eda8a0173625fcdb5f183f96e1008cd; 8195136669661fdfe54e9a8923c33b31c92fc1da up to, but not including, 1336b579f6079fb8520be03624fcd9ba443c930b; 6.12 | cc095cd305fddbe25a968e4a78436ff9476cf0f6, 6eaaa67d6998f6c30c462b140db8c062e07ec473, bf50f3285eda8a0173625fcdb5f183f96e1008cd, 1336b579f6079fb8520be03624fcd9ba443c930b |
| Linux | Linux Kernel | 6.12 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.19; 6.19 up to, but not including, 6.19.9; 7.0 | 6.12.78, 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
- 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: sched_ext: Remove redundant css_put() in scx_cgroup_init() The iterator css_for_each_descendant_pre() walks the cgroup hierarchy under cgroup_lock(). It does not increment the reference counts on yielded css structs. According to the cgroup documentation, css_put() should only be used to release a reference obtained via css_get() or css_tryget_online(). Since the iterator does not use either of these to acquire a reference, calling css_put() in the error path of scx_cgroup_init() causes a refcount underflow. Remove the unbalanced css_put() to prevent a potential Use-After-Free (UAF) vulnerability.
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
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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