Bug 2492757 (CVE-2026-53219)

Summary: CVE-2026-53219 kernel: netfilter: x_tables: avoid leaking percpu counter pointers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's netfilter x_tables component. This vulnerability allows for information disclosure due to improper handling of percpu counter pointers during the copying of rule entry headers to userspace. A local attacker could exploit this by causing a fault in a userspace buffer, leading to the exposure of internal kernel memory addresses.
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Description OSIDB Bzimport 2026-06-25 10:04:09 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: x_tables: avoid leaking percpu counter pointers

The native and compat get-entries paths copy the fixed rule entry header
from the kernelized rule blob to userspace before overwriting the entry's
counter fields with a sanitized counter snapshot.

On SMP kernels, entry->counters.pcnt contains the percpu allocation
address used by x_tables rule counters. A caller can provide a userspace
buffer that faults during the initial fixed-header copy after pcnt has
been copied but before the later sanitized counter copy runs. The syscall
then returns -EFAULT while leaving the raw percpu pointer in userspace.

Copy only the fixed entry prefix before counters from the kernelized rule
blob, then copy the sanitized counter snapshot into the counter field.
Apply this ordering to the IPv4, IPv6, and ARP native and compat
get-entries implementations so a fault cannot expose the internal percpu
counter pointer.
Comment 1 Keith Grant 2026-06-25 23:27:45 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062505-CVE-2026-53219-1af4@gregkh/T