CVE-2026-53397 nfsd: fix posix_acl leak on SETACL decode failure

What is CVE-2026-53397?

CVE-2026-53397 is a high-severity memory corruption vulnerability in Linux kernel, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-401

Which versions are affected by CVE-2026-53397?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53397?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-53397 being exploited?

There is no known exploitation of CVE-2026-53397 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-53397, DEBIAN-CVE-2026-53397, GHSA-mpc7-4w3v-v47r, ROOT-OS-DEBIAN-11-CVE-2026-53397, ROOT-OS-UBUNTU-2204-CVE-2026-53397, UBUNTU-CVE-2026-53397.