Severity: High (CVSS 7.5)

Affected Systems: Linux Linux Kernel

Overview

nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget

A high vulnerability identified as CVE-2026-89674 has been disclosed.

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

nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget

The XDR buffer size calculation in nfsd4_ff_encode_layoutget() has
multiple errors that can result in either an out-of-bounds write or
leaking uninitialized kernel memory to the client:

- fh_len doesn't account for XDR padding on the file handle data
- uid and gid lengths use "8 + len" but xdr_encode_opaque() actually
writes "4 + xdr_align_size(len)" bytes
- ds_len omits the flags and stats_collect_hint fields (8 bytes),
while len's header constant overestimates by 8 bytes -- these
partially cancel but leave a net mismatch

The worst case occurs with short strings (e.g. uid=0, gid=0 with an
odd-sized file handle), where the function writes up to 5 bytes past
the reserved XDR buffer. Conversely, when string lengths happen to be
4-byte aligned, the reservation is too large and stale buffer conten...

Risk

CVSS and CISA data indicate the following:

  • Review the OpenCVE and vendor advisory for exploit conditions and impact

OpenCVE Analysis

CVSS v4.0 N/ACVSS v3.1 7.5 HighCVSS v3.0 N/ACVSS v2 N/AKEV noEPSS yesSSVC no

  • OpenCVE title: nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
  • Severity score: High (CVSS 7.5)
  • EPSS score: 0.00168
  • Weaknesses: CWE-805
Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredLow
User InteractionNone
ScopeUnchanged
Confidentiality ImpactHigh
Integrity ImpactHigh
Availability ImpactHigh
Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Required Action

Review the OpenCVE detail page and linked vendor advisory, then apply the vendor-provided update or mitigation for the affected product.

Prioritize systems where the affected product is internet-facing, handles authentication, or runs with elevated privileges.

Verify Updates

Confirm whether your environment uses the affected product(s): Linux Linux Kernel.

After remediation, verify the installed version against the fixed or unaffected versions listed by the vendor.

Temporary Mitigation (if patch is not available)

Use the mitigation published by the vendor. If no vendor mitigation is available, reduce exposure to the affected product, restrict access to trusted users or networks, and increase monitoring until an update can be applied.

Recommendation

  • Use OpenCVE, vendor, and source references as the source of truth for affected versions and remediation
  • Patch or mitigate affected products after confirming exposure in your environment
  • Monitor affected systems for unusual activity until remediation is complete

Support

If you require assistance, please contact our support team.

Immediate action is strongly recommended to protect your infrastructure.

Source Details

Customer Responsibility and Backups

Before applying updates, mitigations, or configuration changes, customers should take and verify current backups or snapshots of affected systems.

Customers are responsible for managing their servers, validating their own backups, testing changes, and ensuring they can restore services if an update or mitigation causes an issue.



Saturday, September 12, 2026

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