Bug 2492847 (CVE-2026-53212)

Summary: CVE-2026-53212 kernel: netfilter: nft_tunnel: fix use-after-free on object destroy
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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 component, specifically within the nft_tunnel module. This vulnerability occurs due to a use-after-free error when an object is destroyed, where memory is prematurely deallocated while still being referenced by queued network packets. This can lead to system instability or a denial of service (DoS) condition, as subsequent operations attempt to access freed memory.
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Description OSIDB Bzimport 2026-06-25 10:08:50 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nft_tunnel: fix use-after-free on object destroy

nft_tunnel_obj_destroy() calls metadata_dst_free() which directly
kfree()s the metadata_dst, ignoring the dst_entry refcount. Packets
that took a reference via dst_hold() in nft_tunnel_obj_eval() and
are still queued (e.g. in a netem qdisc) are left with a dangling
pointer. When these packets are eventually dequeued, dst_release()
operates on freed memory.

Replace metadata_dst_free() with dst_release() so the metadata_dst
is freed only after all references are dropped. The dst subsystem
already handles metadata_dst cleanup in dst_destroy() when
DST_METADATA is set.
Comment 1 Mauro Matteo Cascella 2026-06-25 16:37:46 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062503-CVE-2026-53212-ce23@gregkh/T