CVE-2026-53391: Linux Kernel

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux Kernel: from 4.0, before 5.15.211 (fixed in 5.15.211); from 5.16, before 6.1.177 (fixed in 6.1.177); from 6.2, before 6.6.144 (fixed in 6.6.144); from 6.7, before 6.12.95 (fixed in 6.12.95); from 6.13, before 6.18.38 (fixed in 6.18.38); from 6.19, before 7.1.3 (fixed in 7.1.3)

Published 2026-07-19. Last modified 2026-08-17.