CVE-2026-53391 NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr
A malicious NFS metadata server can cause a kernel crash in Linux NFS clients by sending a zero-length address in a GETDEVICEINFO response.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53391?
CVE-2026-53391 is a high-severity 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:
NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr
nfs4_decode_mp_ds_addr() decodes the r_netid and r_addr opaques of a netaddr4 from a GETDEVICEINFO multipath-DS body, then immediately calls strrchr(buf, '.') to locate the port separator. Both decodes use xdr_stream_decode_string_dup(), and the current code checks only "nlen < 0" / "rlen < 0" before dereferencing the returned string.
When the on-wire opaque has length zero, xdr_stream_decode_opaque_inline() returns 0 and xdr_stream_decode_string_dup() falls through to its "*str = NULL; return ret" tail, leaving buf NULL with a return value of 0. The "< 0" check does not catch this, and the next line is strrchr(NULL, '.'), a kernel NULL pointer dereference reachable from any pNFS-flexfile client mounted against a malicious or compromised metadata server.
Reject the zero-length cases explicitly so the decoder fails with -EBADMSG (treated as a malformed GETDEVICEINFO body) instead of panicking the client.
Weakness: CWE-476
Which versions are affected by CVE-2026-53391?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53391?
Apply the vendor's patch.
Is CVE-2026-53391 being exploited?
There is no known exploitation of CVE-2026-53391 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53391, DEBIAN-CVE-2026-53391, GHSA-72jx-g4pr-67hm, ROOT-OS-DEBIAN-11-CVE-2026-53391, ROOT-OS-UBUNTU-2204-CVE-2026-53391, UBUNTU-CVE-2026-53391.