How severe is CVE-2026-63800?

CVE-2026-63800 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-63800 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (41st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-63800?

CVE-2026-63800 primarily affects Linux Linux Kernel. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-63800?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-63800 published?

CVE-2026-63800 was published on 2026-07-19 and last updated on 2026-08-17.

CVE-2026-63800

CVE-2026-63800 is a critical-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 0% (41st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-416
Affected product: Linux Linux Kernel
Published: 2026-07-19
Last modified: 2026-08-17

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).

Frequently asked questions

What is CVE-2026-63800?: 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).
How severe is CVE-2026-63800?: CVE-2026-63800 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-63800 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (41st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-63800?: CVE-2026-63800 primarily affects Linux Linux Kernel. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-63800?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-63800 published?: CVE-2026-63800 was published on 2026-07-19 and last updated on 2026-08-17.

References

Affected products (6)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.11:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.11:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.11:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.11:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.11:rc7:*:*:*:*:*:*

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