CVE-2023-53606 nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

What is CVE-2023-53606?

CVE-2023-53606 is a high-severity denial of service vulnerability in Linux kernel, published on 4 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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

nfsd: clean up potential nfsd_file refcount leaks in COPY codepath

There are two different flavors of the nfsd4_copy struct. One is embedded in the compound and is used directly in synchronous copies. The other is dynamically allocated, refcounted and tracked in the client struture. For the embedded one, the cleanup just involves releasing any nfsd_files held on its behalf. For the async one, the cleanup is a bit more involved, and we need to dequeue it from lists, unhash it, etc.

There is at least one potential refcount leak in this code now. If the kthread_create call fails, then both the src and dst nfsd_files in the original nfsd4_copy object are leaked.

The cleanup in this codepath is also sort of weird. In the async copy case, we'll have up to four nfsd_file references (src and dst for both flavors of copy structure). They are both put at the end of nfsd4_do_async_copy, even though the ones held on behalf of the embedded one outlive that structure.

Change it so that we always clean up the nfsd_file refs held by the embedded copy structure before nfsd4_copy returns. Rework cleanup_async_copy to handle both inter and intra copies. Eliminate nfsd4_cleanup_intra_ssc since it now becomes a no-op.

Which versions are affected by CVE-2023-53606?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2023-53606?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-53606 being exploited?

There is no known exploitation of CVE-2023-53606 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2023-53606, DEBIAN-CVE-2023-53606, GHSA-vqjq-cm24-xjp3, UBUNTU-CVE-2023-53606.