CVE-2026-63800 pNFS: Fix use-after-free in pnfs_update_layout()

What is CVE-2026-63800?

CVE-2026-63800 is a critical use after free vulnerability in Linux kernel, published on 19 Jul 2026. 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:

pNFS: Fix use-after-free in pnfs_update_layout()

When hitting the NFS_LAYOUT_RETURN branch in pnfs_update_layout(), the code calls pnfs_prepare_to_retry_layoutget(lo). If it succeeds, pnfs_put_layout_hdr(lo) is called before trace_pnfs_update_layout(), which still references 'lo'. This results in a use-after-free when the tracepoint accesses lo's fields.

Fix this by moving the tracepoint call before pnfs_put_layout_hdr(lo).

Weakness: CWE-416

Which versions are affected by CVE-2026-63800?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-63800?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-63800 being exploited?

There is no known exploitation of CVE-2026-63800 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-2026-63800, DEBIAN-CVE-2026-63800, GHSA-fjxq-h4gg-vf5r, ROOT-OS-DEBIAN-11-CVE-2026-63800, ROOT-OS-UBUNTU-2204-CVE-2026-63800, UBUNTU-CVE-2026-63800.