Linux: Use After Free
CVE-2026-45837 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 723b9fa930cc277c15ce6b9ec9feec828cfac9d7, d18099f19e53250f8ad2801498b88cec29d9107a, 201128fcc7b213d27ab77bc4e89488b41796480f 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 0.12% 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 723b9fa930cc277c15ce6b9ec9feec828cfac9d7 or d18099f19e53250f8ad2801498b88cec29d9107a or 201128fcc7b213d27ab77bc4e89488b41796480f or 4fddde2a732de60bb97e3307d4eb69ac5f1d2b74, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.88 or 6.18.30 or 7.0.7, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 317460317a02a1af512697e6e964298dedd8a163 up to, but not including, 723b9fa930cc277c15ce6b9ec9feec828cfac9d7; 317460317a02a1af512697e6e964298dedd8a163 up to, but not including, d18099f19e53250f8ad2801498b88cec29d9107a; 317460317a02a1af512697e6e964298dedd8a163 up to, but not including, 201128fcc7b213d27ab77bc4e89488b41796480f; 317460317a02a1af512697e6e964298dedd8a163 up to, but not including, 4fddde2a732de60bb97e3307d4eb69ac5f1d2b74; 6.9 | 723b9fa930cc277c15ce6b9ec9feec828cfac9d7, d18099f19e53250f8ad2801498b88cec29d9107a, 201128fcc7b213d27ab77bc4e89488b41796480f, 4fddde2a732de60bb97e3307d4eb69ac5f1d2b74 |
| Linux | Linux Kernel | 6.9 up to, but not including, 6.12.88; 6.13 up to, but not including, 6.18.30; 6.19 up to, but not including, 7.0.7 | 6.12.88, 6.18.30, 7.0.7 |
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 NVD.
Official description
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix use-after-free in arena_vm_close on fork arena_vm_open() only bumps vml->mmap_count but never registers the child VMA in arena->vma_list. The vml->vma always points at the parent VMA, so after parent munmap the pointer dangles. If the child then calls bpf_arena_free_pages(), zap_pages() reads the stale vml->vma triggering use-after-free. Fix this by preventing the arena VMA from being inherited across fork with VM_DONTCOPY, and preventing VMA splits via the may_split callback. Also reject mremap with a .mremap callback returning -EINVAL. A same-size mremap(MREMAP_FIXED) on the full arena VMA reaches copy_vma() through the following path: check_prep_vma() - returns 0 early: new_len == old_len skips VM_DONTEXPAND check prep_move_vma() - vm_start == old_addr and vm_end == old_addr + old_len so may_split is never called move_vma() copy_vma_and_data() copy_vma() vm_area_dup() - copies vm_private_data (vml pointer) vm_ops->open() - bumps vml->mmap_count vm_ops->mremap() - returns -EINVAL, rollback unmaps new VMA The refcount ensures the rollback's arena_vm_close does not free the vml shared with the original VMA.
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
- 8.1 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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