CyberSecBulletin
CVE-2026-64379NVD status: Modified

In the Linux kernel, the following vulnerability has been resolved: smb: client: mask…

Published Updated By the CyberSecBulletin desk

CVE-2026-64379 is a high-severity improper input validation vulnerability in Linux, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14, ee2216dbdf0c677e89bb43e03247dba590ed00ef, f511807feee7cb29b61bdfa86472c7e9e2e5df94 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.31% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14 or ee2216dbdf0c677e89bb43e03247dba590ed00ef or f511807feee7cb29b61bdfa86472c7e9e2e5df94 or 08c600b7e1818539ba5efee4cdb06215c245ca78, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.261 or 5.15.212 or 6.1.178 or 6.6.145, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  4. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxe2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, 5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, ee2216dbdf0c677e89bb43e03247dba590ed00ef; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, f511807feee7cb29b61bdfa86472c7e9e2e5df94; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, 08c600b7e1818539ba5efee4cdb06215c245ca78; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, b84e002e0df26bbc6cbd3ca01b8212601fe0ae7d; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, c6c484a7d5bff6b929a86d7ed5130f29834c6a0d; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, f80add1bfb3425100a325b14f19648e75669a954; e2f8fbfb8d09c06decde162090fac3ee220aa280 up to, but not including, e3d9c7160d483fc8f9e225aafad8ecbbc43f3151; and 1 more ranges5f6f2241034f189c69d4d0b5f8fe24a0c25b0c14, ee2216dbdf0c677e89bb43e03247dba590ed00ef, f511807feee7cb29b61bdfa86472c7e9e2e5df94, 08c600b7e1818539ba5efee4cdb06215c245ca78, b84e002e0df26bbc6cbd3ca01b8212601fe0ae7d, c6c484a7d5bff6b929a86d7ed5130f29834c6a0d
LinuxLinux Kernel5.4 up to, but not including, 5.10.261; 5.11 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; 7.25.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: smb: client: mask server-provided mode to 07777 in modefromsid When modefromsid is active, parse_dacl() applies the server-provided sub_auth[2] value from the NFS mode SID to cf_mode without masking to 07777. Apply the correct masking, same as in the read path.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How developers prevent this class of flaw

  • Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build recognizers for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses.
  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

More Improper Input Validation vulnerabilities (CWE-20)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Input Validation vulnerabilities

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