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Linux Kernel CVE-2026-53391

| EUVDEUVD-2026-45513 HIGH
NULL Pointer Dereference (CWE-476)
2026-07-19 Linux GHSA-72jx-g4pr-67hm
Linux Denial Of Service Null Pointer Dereference
7.5
CVSS 3.1 · Vendor: Linux
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Severity by source

Vendor (Linux) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
7.5 HIGH

Server-to-client crash needs no client credentials (PR:N) and a single crafted response (AC:L, AV:N); only availability is impacted (A:H), C/I:N, with no scope change.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
6.2 MEDIUM
AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat
7.0 MEDIUM
qualitative

Primary rating from Vendor (Linux).

CVSS VectorVendor: Linux

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

5
Analysis Generated
Jul 20, 2026 - 18:08 vuln.today
CVSS changed
Jul 20, 2026 - 15:22 NVD
7.5 (HIGH)
Patch available
Jul 19, 2026 - 14:17 EUVD
CVE Published
Jul 19, 2026 - 12:01 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 19, 2026 - 12:01 cve.org
HIGH 7.5

DescriptionCVE.org

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.

AnalysisAI

Remote denial of service in the Linux kernel's NFSv4/pNFS flexfiles client allows a malicious or compromised NFS metadata server to crash any mounted client by returning a GETDEVICEINFO response containing a zero-length r_addr or r_netid opaque. The decoder nfs4_decode_mp_ds_addr() only checks for negative lengths, so a zero-length value leaves the buffer pointer NULL and the subsequent strrchr(NULL, '.') triggers a kernel NULL-pointer dereference and panic. There is no public exploit identified at time of analysis, and EPSS is low (0.17%, 7th percentile), consistent with a targeted server-side trust attack rather than mass exploitation.

Technical ContextAI

The flaw lives in the pNFS (parallel NFS) flexfiles layout driver within the Linux kernel NFSv4 client. When a client requests device information (GETDEVICEINFO) for a multipath data server, the server returns a netaddr4 structure containing r_netid (transport identifier, e.g. 'tcp') and r_addr (the IP/port string). Both fields are decoded with xdr_stream_decode_string_dup(), which for a zero-length on-wire opaque falls through to setting *str = NULL and returning 0. The code guarded only against a negative return ('nlen < 0' / 'rlen < 0'), so a legitimate-looking zero-length field slips past and the very next operation, strrchr(buf, '.') to find the port separator, dereferences NULL. The root cause class is CWE-476 (NULL Pointer Dereference); the input CWE field is marked N/A but the description unambiguously describes a NULL deref. The fix rejects zero-length cases explicitly, returning -EBADMSG so the malformed body is handled gracefully instead of panicking.

RemediationAI

Vendor-released patch: update to a fixed stable kernel - 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38, 7.1.3, or mainline 7.2-rc1 (or later), which add explicit zero-length rejection returning -EBADMSG. Apply your distribution's kernel security update as the primary fix and reboot; the patched commits are available at git.kernel.org/stable/c/76b94cbd32aacf36a641956385a852635c6802b9 and the sibling stable commits in the references. Where immediate patching is not possible, the concrete compensating control is to avoid or restrict use of pNFS flexfiles: mount NFS with a layout type that avoids the flexfiles device-info path, or ensure clients only mount pNFS from trusted, controlled metadata servers within your security boundary (network-restrict or firewall client access so it cannot reach untrusted NFS metadata servers). The trade-off is that disabling pNFS flexfiles removes the parallel-I/O performance benefit for those mounts, and network restrictions may complicate legitimate multi-server NFS deployments. Consult the advisory at https://nvd.nist.gov/vuln/detail/CVE-2026-53391 and vuldb.com/vuln/380126 for tracking.

Same weakness CWE-476 – NULL Pointer Dereference

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected

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CVE-2026-53391 vulnerability details – vuln.today
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