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Linux Kernel CVE-2026-53392

| EUVDEUVD-2026-45514 HIGH
NULL Pointer Dereference (CWE-476)
2026-07-19 Linux GHSA-3gfh-mq5v-c264
Denial Of Service Linux Null Pointer Dereference
7.5
CVSS 3.1 · Vendor: Linux
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Control or impersonate pNFS flexfiles server
  2. Delivery
    Victim client mounts flexfiles layout
  3. Exploit
    Return layout with fh_count=0
  4. Execution
    Client stores ZERO_SIZE_PTR in fh_versions
  5. Persist
    Layoutreturn encoding dereferences sentinel
  6. Impact
    Kernel null-ptr-deref panic (DoS)

Vulnerability Assessment

Weakness
CWE
CWE-476
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Null pointer safety, defensive checks
MITRE ATT&CK

1 technique across 1 tactic: Impact

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Exploitation requires the victim to be a Linux NFSv4.1/4.2 client using pNFS with the flexfiles layout type (CONFIG_PNFS_FLEXFILE_LAYOUT), mounting from an NFS server that the attacker controls, has compromised, or can impersonate/MITM on the network path. The concrete trigger is a malformed flexfiles layout body whose decoded filehandle-version count equals zero, reaching ff_layout_alloc_lseg(); the crash then fires during ff_layout_encode_ff_layoutupdate/layoutreturn encoding. Limiting factors: the target host must actually mount pNFS flexfiles (a non-default, uncommon configuration), the attacker must sit on the server side of the NFS session, and impact is limited to a kernel panic/DoS - no code execution or data disclosure. This is not exploitable against default Linux installs that do not use pNFS flexfiles.
Impact

The supplied CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H = 7.5) rates this as a network, unauthenticated, availability-only DoS. In practice the network vector is real but constrained: the impact is only triggered when a Linux client mounts a pNFS NFSv4.1/4.2 flexfiles layout from a server that returns a crafted layout, so exploitation requires the attacker to control or impersonate the NFS server the victim connects to - a meaningful precondition that the raw AC:L understates. No EPSS score, KEV listing, or public POC was provided, so this is not a confirmed in-the-wild threat; the presence of a KASAN/QEMU reproducer in the upstream commit means a working trigger exists but is not a weaponized exploit. Note a data conflict: the intelligence Tags label this 'Information Disclosure', but the CVSS impact metrics are C:N/I:N/A:H, i.e. pure availability/crash - the tag appears mislabeled and should not be treated as evidence of data leakage. Overall this is a moderate-priority patch: genuine DoS/panic risk for hosts using pNFS flexfiles against untrusted servers, low-to-negligible risk for the vast majority of Linux systems that never use flexfiles.
Exploit ScenarioDerived

An attacker who operates a malicious NFS server, or who can MITM/impersonate a legitimate pNFS flexfiles server on the network, waits for a Linux client to mount a flexfiles-backed export. The server returns a crafted flexfiles layout with a filehandle-version count of zero; when the client later encodes a layoutreturn it dereferences the ZERO_SIZE_PTR and the kernel panics, crashing the host. A KASAN/QEMU reproducer demonstrating the null-ptr-deref is included in the upstream commit, but no weaponized public exploit is known.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 20, 2026

Remote denial-of-service in the Linux kernel NFSv4 flexfiles (pNFS) client allows a malicious or compromised NFS server to crash a mounting client via a malformed flexfiles layout that declares a zero filehandle-version count. The flaw stems from ff_layout_alloc_lseg() accepting fh_count == 0, which produces a ZERO_SIZE_PTR that is later dereferenced during layoutreturn encoding, triggering a null-pointer-deref and kernel panic. No public exploit identified at time of analysis, though the commit includes a QEMU/KASAN reproducer; CVSS 7.5 reflects availability-only impact (A:H) with no confidentiality or integrity effect.

RemediationAI

Vendor-released patch: upgrade to Linux kernel 6.12.96, 6.18.38, 7.1.3, or 7.2-rc1 (or your distribution's backported build carrying stable commits 7779c85028a0 / d8c90c7cc061 / 2131ed64b767 / 2c6bb3c40bc2 from git.kernel.org/stable). The fix adds a fh_count == 0 rejection before allocation, matching the existing GETDEVICEINFO zero-version_count validation. If you cannot patch immediately, the practical compensating control is to avoid the vulnerable code path: only mount NFS shares from trusted, authenticated servers and avoid pNFS flexfiles layouts from untrusted sources - mount with NFSv3 or a non-flexfiles/non-pNFS configuration where operationally acceptable (side effect: loss of pNFS parallel-I/O performance benefits), and enforce Kerberos (sec=krb5) plus network segmentation so an attacker cannot impersonate or MITM the NFS server (side effect: added Kerberos administration overhead). Blocking or restricting client access to only known-good NFS server IPs on ports 2049/111 further reduces exposure. Consult the referenced kernel.org stable commit URLs and your distro's advisory for the exact backport version applicable to your kernel series.

Affected VersionsENISA

Linux patch: 6.12.96
Linux d67ae825a59d639e4d8b82413af84d854617a87e <d8c90c7cc061265d5f2813a1f5c82ef2f4707e67
Linux d67ae825a59d639e4d8b82413af84d854617a87e <2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2
Linux 4.0
Linux patch: 7.2-rc1
Linux patch: 7.1.3
Linux d67ae825a59d639e4d8b82413af84d854617a87e <7779c85028a0676fb190cde4f0c540f4f8e97761
Linux patch: 6.18.38
Linux patch: 0
Linux d67ae825a59d639e4d8b82413af84d854617a87e <2131ed64b767ffa8bcdb3677d90f3964e39aabc8

Affected Packages

euvd linux no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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Technical ContextAI · show details

The vulnerable code is in the kernel's NFSv4.x parallel-NFS (pNFS) flexfiles layout driver (fs/nfs/flexfilelayout). When a flexfiles layout is granted, ff_layout_alloc_lseg() XDR-decodes a per-mirror data-storage-server descriptor that contains an array of filehandle versions; the decoded count is passed directly to kzalloc_objs() as the object count. The pre-patch logic only checked for a NULL return, but a count of zero causes the kernel slab allocator to return ZERO_SIZE_PTR (0x10-region sentinel) rather than NULL. That sentinel is stored in dss_info->fh_versions, and downstream flexfiles code such as ff_layout_encode_ff_layoutupdate() assumes at least one filehandle version exists, dereferencing the sentinel. The CWE was not assigned in the input, but the root cause is a NULL/sentinel-pointer dereference (CWE-476) arising from missing input validation (CWE-20) of an attacker-controlled length field. Affected CPEs are cpe:2.3:a:linux:linux (kernel), specifically builds with CONFIG_PNFS_FLEXFILE_LAYOUT and clients that actually mount pNFS flexfiles exports. The fix mirrors an existing zero-version_count check already present in the flexfiles GETDEVICEINFO parser.

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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 5.9 MEDIUM

Network-triggered crash but requires attacker-controlled/impersonated NFS server and a client using pNFS flexfiles, so AC:H; impact is availability-only (kernel panic), hence C:N/I:N/A:H.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE 6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Red Hat 7.0 MEDIUM

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

4
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/flexfiles: reject zero filehandle version count

ff_layout_alloc_lseg() decodes the filehandle-version array count from the flexfiles layout body. The value is used as the count for kzalloc_objs(), and the current code only rejects NULL.

A zero count yields ZERO_SIZE_PTR, which can be stored in dss_info->fh_versions even though later flexfiles paths assume that at least one filehandle version exists.

Reject fh_count == 0 before the allocation, matching the existing zero version_count validation in the flexfiles GETDEVICEINFO parser.

A QEMU/KASAN run with a malformed flexfiles layout hit:

KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750 ff_layout_encode_layoutreturn+0x683/0x970 nfs4_xdr_enc_layoutreturn+0x278/0x3a0 Kernel panic - not syncing: Fatal exception

The patched kernel rejects the malformed layout without KASAN/oops/panic, and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.

Executive ViewAI

Why It Matters

The Linux kernel NFSv4 flexfiles client vulnerability (CVE-2026-53392) allows a malicious NFS server to remotely crash client systems, disrupting access to network-attached storage. This affects any organization using Linux-based systems with NFSv4 pNFS client deployments, potentially impacting availability of applications and services dependent on NFS storage. Patching is available and should be prioritized for systems in this configuration.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.2%
Top 94% exploitable
Prevalence
High
Linux kernel ubiquitous, but vulnerable pNFS flexfiles client config is uncommon
Data Quality
6 sources
Confidence: High
EUVD NVD CVE.org EPSS MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
High

Priority Score

38
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Null Pointer Dereference MEDIUM

A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Same weakness CWE-476 – NULL Pointer Dereference

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Same technique Denial Of Service

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CVE-2015-5119 CRITICAL POC
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CVE-2011-2462 CRITICAL POC
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CVE-2011-0611 HIGH POC
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CVE-2012-1889 HIGH POC
8.8
CVE-2012-0507 CRITICAL POC
9.8
CVE-2014-1761 HIGH POC
7.8
CVE-2015-5122 CRITICAL POC
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CVE-2011-0609 HIGH POC
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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

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-53392 ADVISORY https://seclists.org/oss-sec/2026/q3/230 ADVISORY https://ubuntu.com/security/notices/USN-8726-1 ADVISORY https://ubuntu.com/security/notices/USN-8727-1 ADVISORY https://vuldb.com/vuln/380127 REF https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf REF https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8 REF https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2 REF https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761 REF https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f REF https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc REF https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67 REF https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04

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