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NVD / CVE Program· CNA Linux

CVE-2026-68388: smb/client: handle overlapping allocated ranges in fallocate

Noroxi assessment

Priority: Monitor (action score 39/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.51% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 01719883235507b1585e4c51e320d9a7113dc698, 377fe3e583e46369ee1004d5cfe12271d6589a68, 437637f5ff3f573b2edf8571de91fb00a21eb4e6; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 01719883235507b1585e4c51e320d9a7113dc698, 377fe3e583e46369ee1004d5cfe12271d6589a68, 437637f5ff3f573b2edf8571de91fb00a21eb4e6; azl3 kernel 6.6.143.1-1 on Azure Linux 3.0 6.6.150.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: smb/client: handle overlapping allocated ranges in fallocate smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC. The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset. For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200): Request: [100, 400) Server range: [ 0, 200) allocated Correct: [100, 200) allocated data, skip [200, 400) hole, zero-fill Current: [100, 300) skipped [300, 400) zero-filled afterwards The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled. Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows. This also prevents a malformed range length from causing an out-of-bounds zero-buffer read.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Aug 10, 2026
Updated
Oct 19, 2026
EPSS
0.5% · 43th percentile

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
9.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • No public exploit code on record
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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2f9f4a2d0e6fcf0673ed51195e06e47abe966900, 5e397c943424de94879830e72c95f2679e297a76, 5.14affected
    • c406bb9ece6ef63721daab106f132ff4b4234e81 and later · before aeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before 01719883235507b1585e4c51e320d9a7113dc698affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before f47c7277c03a636fcc3a57969f2dc09567b3c050affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before 437637f5ff3f573b2edf8571de91fb00a21eb4e6affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before 377fe3e583e46369ee1004d5cfe12271d6589a68affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before 7e08ab7a061b17ac1989a225c6afb53f44a86808affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before a4a09e5142835633fffbde68bd0a039ba4d4bf97affected · git
    • 966a3cb7c7db786452a87afdc3b48858fc4d4d6b and later · before b09ae45d85dc816987a71db9eebc54b0ae288e94affected · git
    • 5.10.50 and later · before 5.10.265affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.157.1.el8_104.18.0-553.157.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10
AlmaLinux:8kernel-rt-modulesbefore 4.18.0-553.157.1.rt7.498.el8_104.18.0-553.157.1.rt7.498.el8_10

+66

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-68384Aug 10, 2026 · drm/xe/vf: Fix VF CCS attach/detach race with in-flight BO moves
    31Monitor
  • ← EarlierCVE-2026-68385Aug 10, 2026 · s390/checksum: Fix csum_partial() without vector facility
    39Monitor
  • Later →CVE-2026-68391Aug 10, 2026 · Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux01719883235507b1585e4c51e320d9a7113dc698Vendor (CNA)
Linux Linux377fe3e583e46369ee1004d5cfe12271d6589a68Vendor (CNA)
Linux Linux437637f5ff3f573b2edf8571de91fb00a21eb4e6Vendor (CNA)
Linux Linux5.10.265Vendor (CNA)
Linux Linux5.13Vendor (CNA)
Linux Linux5.14Vendor (CNA)
Linux Linux7e08ab7a061b17ac1989a225c6afb53f44a86808Vendor (CNA)
Linux Linuxa4a09e5142835633fffbde68bd0a039ba4d4bf97Vendor (CNA)
Linux Linuxaeb58a4eb39a7ff4d7782b4f4ada0fda5e0675d2Vendor (CNA)
Linux Linuxb09ae45d85dc816987a71db9eebc54b0ae288e94Vendor (CNA)
Linux Linuxf47c7277c03a636fcc3a57969f2dc09567b3c050Vendor (CNA)
azl3 kernel 6.6.143.1-1 on Azure Linux 3.06.6.150.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:bpftool4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.157.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.101-1~deb12u1 · Debian:12Package registry (OSV)
red hat:bpftool0:4.18.0-553.157.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-553.157.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-553.157.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-553.157.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)

+10

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-681600 days apartceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()
    39Monitor
  • CVE-2026-680822 days apartlibceph: fix two unsafe bare decodes in decode_lockers()
    39Monitor
  • CVE-2026-720845 days apartscsi: target: Bound PR-OUT TransportID parsing to the received buffer
    39Monitor
  • CVE-2026-683430 days apartsmb: client: validate DFS referral PathConsumed
    36Monitor
  • CVE-2026-6455114 days apartsctp: validate STALE_COOKIE cause length before reading staleness
    36Monitor
  • CVE-2026-680980 days apartksmbd: bound DACL dedup walk to copied ACEs
    35Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records