CVE-2026-53396 (GCVE-0-2026-53396)

Vulnerability from cvelistv5 – Published: 2026-07-19 12:01 – Updated: 2026-08-17 04:50
VLAI
Title
nfsd: fix posix_acl leak and ignored error in nfsd4_create_file
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix posix_acl leak and ignored error in nfsd4_create_file nfsd4_create_file() has two bugs in its ACL handling: The return value of nfsd4_acl_to_attr() is silently discarded. When the NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for unsupported ACE types), the file is created without any ACL and the client receives NFS4_OK. This violates RFC 7530/8881 which require the server to reject unsupported attributes on CREATE. When start_creating() fails after ACL attributes have been populated in attrs (either via nfsd4_acl_to_attr or via ownership transfer from open->op_dpacl/op_pacl), the function jumps to out_write which skips nfsd_attrs_free(). The posix_acl allocations are leaked. A client can trigger this repeatedly with OPEN(CREATE), ACL attributes, and an invalid filename (e.g., longer than NAME_MAX). Fix both by capturing the nfsd4_acl_to_attr() return value and by changing the early error paths to jump to out instead of out_write. Initialize child to ERR_PTR(-EINVAL) so that end_creating() is safe to call even if start_creating() was never reached.
Severity
7.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7ab96df840e60eb933abfe65fc5fe44e72f16dc0 , < 18cf006a08babec0bbac2a3784f8f28e56e47490 (git)
Affected: 7ab96df840e60eb933abfe65fc5fe44e72f16dc0 , < 24c975bbdd564d7d0ad90294bfa69729830345de (git)
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Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.1.3 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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              "value": "AV:N - The vulnerable code is reached via NFSv4 OPEN(CREATE) handled by nfsd over the network (RPC on TCP/2049), from nfsd4_proc_compound() through nfsd4_open() and do_open_lookup() into nfsd4_create_file().\nAC:L - An authenticated NFS client can reliably trigger the leak by sending OPEN(CREATE) with ACL attributes and a filename that causes start_creating() to fail (e.g., longer than the backing filesystem NAME_MAX); no race or attacker-uncontrollable conditions are required.\nPR:L - Exploitation requires an authenticated NFS client with write/create permission on the target export directory (enforced by fh_verify()/nfsd_permission), which maps to basic authorized-user access rather than unauthenticated or server-admin privileges.\nUI:N - No victim interaction is needed beyond the attacker sending crafted NFSv4 compound requests to the server.\nS:U - Impact is confined to kernel memory management and exported file metadata within the NFS server\u0027s security authority; it does not cross VM, container, or IOMMU boundaries.\nC:N - The bug is a refcount leak of posix_acl kernel objects with no out-of-bounds read, use-after-free, or other mechanism that exposes kernel memory to the attacker.\nI:L - The ignored nfsd4_acl_to_attr() error allows files to be created without the requested ACL while returning NFS4_OK, causing limited but incorrect modification of exported file security attributes on shared storage.\nA:H - Repeated triggering leaks unbounded posix_acl slab objects per request, enabling sustained kernel memory exhaustion that can deny NFS service and degrade overall system availability."
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}



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