CVE-2026-53000

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nat: use kfree_rcu to release ops

Florian Westphal says:

Historically this is not an issue, even for normal base hooks: the data path doesnt use the original nf_hook_ops that are used to register the callbacks.

However, in v5.14 I added the ability to dump the active netfilter hooks from userspace.

This code will peek back into the nf_hook_ops that are available at the tail of the pointer-array blob used by the datapath.

The nat hooks are special, because they are called indirectly from the central nat dispatcher hook. They are currently invisible to the nfnl hook dump subsystem though.

But once that changes the nat ops structures have to be deferred too.

Update nf_nat_register_fn() to deal with partial exposition of the hooks from error path which can be also an issue for nfnetlink_hook.

Weakness

The product attempts to return a memory resource to the system, but it calls the wrong release function or calls the appropriate release function incorrectly.

Affected Software

Extended Description

This weakness can take several forms, such as:

Potential Mitigations

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, glibc in Linux provides protection against free of invalid pointers.

References

• https://git.kernel.org/stable/c/32fdd2e38e7435a368d88f5977a7d6585ebc8b0e
• https://git.kernel.org/stable/c/3c7511f38ab511b791196b13ae48bf4973bf7dfd
• https://git.kernel.org/stable/c/6eda0d771f94267f73f57c94630aa47e90957915
• https://access.redhat.com/security/cve/CVE-2026-53000
• https://bugzilla.redhat.com/show_bug.cgi?id=2492273
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53000.json