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.

Project Subscriptions

Vendors Products
Linux Kernel Subscribe
Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8566-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8568-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8569-1 Linux kernel (HWE) vulnerabilities
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 28 May 2026 02:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416

Thu, 28 May 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-825
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Important


Wed, 27 May 2026 13:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416

Wed, 27 May 2026 10:30:00 +0000

Type Values Removed Values Added
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.
Title bpf: Fix use-after-free in arena_vm_close on fork
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-06-14T17:46:01.781Z

Reserved: 2026-05-13T15:03:33.077Z

Link: CVE-2026-45837

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-27T11:16:23.020

Modified: 2026-06-17T10:52:34.930

Link: CVE-2026-45837

cve-icon Redhat

Severity : Important

Publid Date: 2026-05-27T00:00:00Z

Links: CVE-2026-45837 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-28T03:45:06Z

Weaknesses