CVE-2026-53212

Analyzed Analyzed - Analysis Complete

Use-After-Free in Linux Kernel nft_tunnel

Publication date: 2026-06-25

Last updated on: 2026-07-02

Assigner: kernel.org

Description

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-06-25

Last Modified

2026-07-02

Generated

2026-07-15

AI Q&A

2026-06-25

EPSS Evaluated

2026-07-14

NVD

CVE-2026-53212

EUVD

EUVD-2026-39303

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	7.1
linux	linux_kernel	7.1
linux	linux_kernel	7.1
linux	linux_kernel	7.1
linux	linux_kernel	From 5.16 (inc) to 6.1.176 (exc)
linux	linux_kernel	From 6.2 (inc) to 6.6.143 (exc)
linux	linux_kernel	From 5.11 (inc) to 5.15.210 (exc)
linux	linux_kernel	From 4.19 (inc) to 5.10.259 (exc)
linux	linux_kernel	From 6.13 (inc) to 6.18.36 (exc)
linux	linux_kernel	From 6.7 (inc) to 6.12.94 (exc)
linux	linux_kernel	From 6.19 (inc) to 7.0.13 (exc)
linux	linux_kernel	7.1
linux	linux_kernel	7.1

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-416	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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free issue in the Linux kernel's netfilter nft_tunnel component. Specifically, the function nft_tunnel_obj_destroy() improperly frees memory by calling metadata_dst_free(), which ignores the reference count of the metadata_dst object. As a result, packets that still hold references to this object but are queued (for example, in a netem qdisc) end up with dangling pointers. When these packets are later processed, the system attempts to access memory that has already been freed, leading to undefined behavior.

The fix replaces metadata_dst_free() with dst_release(), ensuring that the metadata_dst object is only freed after all references to it are dropped, preventing the use-after-free condition.

Mitigation Strategies

The vulnerability is fixed by replacing the use of metadata_dst_free() with dst_release() in the nft_tunnel_obj_destroy() function to ensure proper reference counting and memory management.

Immediate mitigation steps include updating the Linux kernel to a version where this fix is applied, as the issue involves kernel-level memory management in the netfilter nft_tunnel subsystem.

Impact Analysis

This use-after-free vulnerability can lead to system instability or crashes due to accessing freed memory. It may also be exploitable by attackers to execute arbitrary code or cause denial of service, depending on the context in which the freed memory is accessed.

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