Linux: Use After Free
CVE-2026-43379 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 bf4d66d72e4a9e268c1012c331ce9eaedb5e2086, 960699317d39f46611f4ebeb69edc567c1f4e6b6, dbbd328cf58261ca239756fe1c0d10c9518d3399 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 bf4d66d72e4a9e268c1012c331ce9eaedb5e2086 or 960699317d39f46611f4ebeb69edc567c1f4e6b6 or dbbd328cf58261ca239756fe1c0d10c9518d3399 or b3568347c51c46e2cabc356bc34676df98296619, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.130 or 6.12.78 or 6.18.19 or 6.19.9, 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 | 27b40b7bfcd121fe13a150ffe11957630cf49246 up to, but not including, bf4d66d72e4a9e268c1012c331ce9eaedb5e2086; 5fb282ba4fef8985a5acf2b32681f2ec07732561 up to, but not including, 960699317d39f46611f4ebeb69edc567c1f4e6b6; 5fb282ba4fef8985a5acf2b32681f2ec07732561 up to, but not including, dbbd328cf58261ca239756fe1c0d10c9518d3399; 5fb282ba4fef8985a5acf2b32681f2ec07732561 up to, but not including, b3568347c51c46e2cabc356bc34676df98296619; 5fb282ba4fef8985a5acf2b32681f2ec07732561 up to, but not including, eac3361e3d5dd8067b3258c69615888eb45e9f25; 6.6.32 up to, but not including, 6.6.130; 6.9 | bf4d66d72e4a9e268c1012c331ce9eaedb5e2086, 960699317d39f46611f4ebeb69edc567c1f4e6b6, dbbd328cf58261ca239756fe1c0d10c9518d3399, b3568347c51c46e2cabc356bc34676df98296619, eac3361e3d5dd8067b3258c69615888eb45e9f25, 6.6.130 |
| Linux | Linux Kernel | 6.6.32 up to, but not including, 6.6.130; 6.9 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 | 6.6.130, 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
- 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 in smb_lazy_parent_lease_break_close() opinfo pointer obtained via rcu_dereference(fp->f_opinfo) is being accessed after rcu_read_unlock() has been called. This creates a race condition where the memory could be freed by a concurrent writer between the unlock and the subsequent pointer dereferences (opinfo->is_lease, etc.), leading to a use-after-free.
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/960699317d39f46611f4ebeb69edc567c1f4e6b6
- git.kernel.org/stable/c/b3568347c51c46e2cabc356bc34676df98296619
- git.kernel.org/stable/c/bf4d66d72e4a9e268c1012c331ce9eaedb5e2086
- git.kernel.org/stable/c/dbbd328cf58261ca239756fe1c0d10c9518d3399
- git.kernel.org/stable/c/eac3361e3d5dd8067b3258c69615888eb45e9f25
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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