CVE-2026-53397
Received Received - Intake

Memory Leak in Linux Kernel NFS Server

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix posix_acl leak on SETACL decode failure nfsaclsvc_decode_setaclargs() and nfs3svc_decode_setaclargs() each call nfs_stream_decode_acl() twice, first for NFS_ACL and then for NFS_DFACL. Each successful call transfers ownership of a freshly allocated posix_acl into argp->acl_access or argp->acl_default. If the first call succeeds but the second fails, the decoder returns false and argp->acl_access is left dangling. ACLPROC2_SETACL.pc_release was wired to nfssvc_release_attrstat and ACLPROC3_SETACL.pc_release was wired to nfs3svc_release_fhandle. Both only call fh_put() and have no knowledge of the ACL fields on argp. The posix_acl_release() pairs sat at the out: labels inside nfsacld_proc_setacl() and nfsd3_proc_setacl(), but svc_process() skips pc_func when pc_decode returns false, so that cleanup is unreachable on decode failure: svc_process_common() pc_decode() /* decode_setaclargs: false */ /* pc_func skipped */ pc_release() /* fh_put only -- ACLs leaked */ The orphaned posix_acl is leaked for the lifetime of the server. Fix by adding nfsaclsvc_release_setacl() and nfs3svc_release_setacl(), which release both argp->acl_access and argp->acl_default in addition to fh_put(), and wiring them as pc_release for their respective SETACL procedures. pc_release runs on every path svc_process() takes after decode, including decode failure, so the posix_acl_release() pairs are removed from the proc functions' out: labels to keep ownership in one place. This matches the existing release_getacl() pattern used by the sibling GETACL procedures.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-53397
EUVD
EUVD-2026-45519

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a memory leak in the NFS (Network File System) service. When processing SETACL requests, the system fails to properly release allocated memory for access control lists (ACLs) if an error occurs during decoding. This leads to a leak of posix_acl structures, which remain allocated for the lifetime of the server.

Detection Guidance

This vulnerability is specific to the Linux kernel's NFS server implementation and does not have a direct network-based detection method. Detection involves checking the kernel version and NFS server configuration for potential exposure. Use commands like 'uname -a' to check the kernel version and 'systemctl status nfs-server' to verify if NFS services are running. If the kernel version is vulnerable and NFS services are active, the system may be affected.

Impact Analysis

The impact is primarily on system stability and resource usage. The leaked memory can accumulate over time, potentially causing the system to run out of memory. This may lead to performance degradation or crashes, especially in environments with high NFS traffic or long-running servers.

Compliance Impact

This vulnerability causes a memory leak in the Linux kernel's NFS server when handling ACL decode failures. While it does not directly impact data confidentiality or integrity, it could lead to resource exhaustion on the server, potentially causing service disruptions. This may indirectly affect compliance with standards like GDPR or HIPAA by reducing system reliability or availability, though no direct data breach or unauthorized access is involved.

Mitigation Strategies

Immediately update the Linux kernel to a patched version that includes the fix for CVE-2026-53397. If updating is not immediately possible, consider disabling the NFS server service temporarily using 'systemctl stop nfs-server' and 'systemctl disable nfs-server' to prevent potential exploitation until the patch is applied.

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