CVE-2026-64379Network attack vector

Service disruption via unmasked SMB mode bits

Published Jul 25, 2026 · Updated Jul 25, 2026

Improper mode validation in the Linux kernel SMB client allows remote attackers to disrupt SMB-backed services through a malicious server. With modefromsid active, parse_dacl() copies server-controlled sub_auth[2] bits from an NFS mode SID into cf_mode without restricting them to 07777. A victim administrator or service must mount the share or access a crafted object; forged inode-type bits can block mounting or make share objects unusable.

CVSS severity7.1
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper mode validation in the Linux kernel SMB client allows remote attackers to disrupt SMB-backed services through a malicious server. With modefromsid active, parse_dacl() copies server-controlled sub_auth[2] bits from an NFS mode SID into cf_mode without restricting them to 07777. A victim administrator or service must mount the share or access a crafted object; forged inode-type bits can block mounting or make share objects unusable.

The record

CVE
CVE-2026-64379
Published
Jul 25, 2026
Updated
Jul 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-279, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.4
  2. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <08c600b7e1818539ba5efee4cdb06215c245ca78
  3. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14
  4. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <b84e002e0df26bbc6cbd3ca01b8212601fe0ae7d
  5. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <c6c484a7d5bff6b929a86d7ed5130f29834c6a0d
  6. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <e3d9c7160d483fc8f9e225aafad8ecbbc43f3151
  7. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <ee2216dbdf0c677e89bb43e03247dba590ed00ef
  8. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <f511807feee7cb29b61bdfa86472c7e9e2e5df94
  9. Affected versionversion=e2f8fbfb8d09c06decde162090fac3ee220aa280 <f80add1bfb3425100a325b14f19648e75669a954

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5.4; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <08c600b7e1818539ba5efee4cdb06215c245ca78; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <b84e002e0df26bbc6cbd3ca01b8212601fe0ae7d; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <c6c484a7d5bff6b929a86d7ed5130f29834c6a0d; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <e3d9c7160d483fc8f9e225aafad8ecbbc43f3151; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <ee2216dbdf0c677e89bb43e03247dba590ed00ef; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <f511807feee7cb29b61bdfa86472c7e9e2e5df94; version=e2f8fbfb8d09c06decde162090fac3ee220aa280 <f80add1bfb3425100a325b14f19648e75669a954

Published CVSS scores

7.0OracleCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.1Linux CNACVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
7.0Red HatCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-279Incorrect Execution-Assigned Permissions
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo