CVE-2026-89671
Received
Received - Intake
Privilege Escalation in Linux Kernel NFS Server
Vulnerability report for CVE-2026-89671, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-11
Last updated on: 2026-09-11
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
nfsd: gate nfs3 setacl by argp->mask
nfsd3_proc_setacl() calls set_posix_acl() unconditionally for both
ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing argp->acl_access and
argp->acl_default verbatim. The NFSv3 ACL decoder only populates
those pointers when the corresponding mask bit is set:
nfs3svc_decode_setaclargs()
if (args->mask & NFS_ACL) decode into acl_access
if (args->mask & NFS_DFACL) decode into acl_default
/* otherwise the pointer stays NULL (pc_argzero) */
nfsd3_proc_setacl()
set_posix_acl(.., ACL_TYPE_ACCESS, argp->acl_access)
set_posix_acl(.., ACL_TYPE_DEFAULT, argp->acl_default)
set_posix_acl(idmap, dentry, type, NULL) is the VFS "remove this
ACL type" operation. A NULL pointer that means "the client did not
send this arm" is therefore indistinguishable from "the client
asked to remove this ACL". A SETACL with mask=NFS_ACL silently
drops the directory's default ACL; mask=0 drops both.
The sibling nfsd3_proc_getacl() already consults argp->mask before
touching each arm; mirror that in setacl.
Fix by wrapping each set_posix_acl() call in the matching mask bit
check and initializing error to 0 before inode_lock so that a
request with neither bit set leaves the on-disk ACLs untouched and
returns nfs_ok. The out_drop_lock path and the unconditional
posix_acl_release() at out: are preserved; both NULL-tolerate the
skipped arms.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
