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NVD / CVE Program· CNA Linux

CVE-2026-64400: ksmbd: prevent path traversal bypass by restricting caseless retry

Noroxi assessment

Priority: Monitor (action score 34/100)

  • 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: 0.44% (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.
  • Fixed version: Linux Linux 21f050439db157f2afcc19885dec14549ca6ffc0, 5.16, 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95.

Low priority for now. Upgrade to Linux Linux 21f050439db157f2afcc19885dec14549ca6ffc0, 5.16, 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95 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: ksmbd: prevent path traversal bypass by restricting caseless retry ksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path resolution within the share root. When a crafted path attempts to escape the share boundary using parent-directory components ('..'), vfs_path_parent_lookup() detects this and immediately fails, returning -EXDEV. However, a bug exists in __ksmbd_vfs_kern_path() under caseless mode. The function fails to intercept the -EXDEV error and erroneously falls through to the caseless retry logic, which is intended only for genuinely missing files. During this retry process, the path is reconstructed, leading to an unintended LOOKUP_BENEATH bypass that allows write-capable users to create zero-length files or directories outside the exported share. Fix this by ensuring that the execution only proceeds to the caseless lookup retry when the error is specifically -ENOENT. Any other errors, such as -EXDEV from a path traversal attempt, must be returned immediately.

HighCVSS 8.6 · v3.1—No exploit Fix available
Published
Jul 25, 2026
Updated
Oct 30, 2026
EPSS
0.4% · 39th percentile
CWE
—

Report tools

JSON

Action score

34

Monitor

Low priority for now.

CVSS
34 / 40 · 8.6 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CNA vs NVD score

NVD
—
CNA · Linux
8.6
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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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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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.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.15.145 and later · before 5.16
  • linux linux kernel6.1.71 and later · before 6.2
  • linux linux kernel6.3.10 and later · before 7.1.4

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

    • 019aae488dbc67c97a33db03652e20e2c9e3afa7, ef6cc1c465786b3e4e735d1ab8b616b3e94402df, 6.4affected
    • 6927ffe7479c72e7ebf885507227266a75f7c97d and later · before 21f050439db157f2afcc19885dec14549ca6ffc0affected · git
    • 74d7970febf7e9005375aeda0df821d2edffc9f7 and later · before eec1dd2586c4016b7555a5d047db2b3756459fb2affected · git
    • 74d7970febf7e9005375aeda0df821d2edffc9f7 and later · before a1c331d98313380c38f616c8b28b890ec8ef9c28affected · git
    • 74d7970febf7e9005375aeda0df821d2edffc9f7 and later · before cfb5a56c218888f9d74165dff0c282cd0be97983affected · git
    • 74d7970febf7e9005375aeda0df821d2edffc9f7 and later · before 8c9a4f1327eb71efbf14842e7b8a6d965077eb67affected · git
    • 74d7970febf7e9005375aeda0df821d2edffc9f7 and later · before 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95affected · git
    • 6.1.71 and later · before 6.1.191affected · semver
    • 5.15.145 and later · before 5.16affected · semver
    • 6.3.10 and later · before 6.4affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-26.12.115-2
Debian:14linuxbefore 7.1.4-17.1.4-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-64391Jul 25, 2026 · ksmbd: use opener credentials for ADS I/O
    39Monitor
  • ← EarlierCVE-2026-64392Jul 25, 2026 · ksmbd: use opener credentials for delete-on-close
    36Monitor
  • Later →CVE-2026-64401Jul 25, 2026 · smb: client: resolve SWN tcon from live registrations
    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 Linux21f050439db157f2afcc19885dec14549ca6ffc0Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux54bab9ba5a9f156ffa9324fcbe5a356fd0242f95Vendor (CNA)
Linux Linux6.1.191Vendor (CNA)
Linux Linux6.4Vendor (CNA)
Linux Linux8c9a4f1327eb71efbf14842e7b8a6d965077eb67Vendor (CNA)
Linux Linuxa1c331d98313380c38f616c8b28b890ec8ef9c28Vendor (CNA)
Linux Linuxcfb5a56c218888f9d74165dff0c282cd0be97983Vendor (CNA)
Linux Linuxeec1dd2586c4016b7555a5d047db2b3756459fb2Vendor (CNA)
debian:linux6.12.115-2 · Debian:13Package registry (OSV)
debian:linux7.1.4-1 · Debian:14Package registry (OSV)

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.

No nightly-computed relations.

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).

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
low · data can be read
Integrity
low · 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
Low
Integrity impact
Low
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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

References

Show all references (5 more)

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

All records