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Linux KernelOperating system · Linux

CVE-2026-31392

HIGH · 8.1 CVSS v3.1 Published 2026-04-03
Fix available
A fix is available. Upgrade to 2.6.33 / 2.6.35 or later.
See remediation →
83/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix krb5 mount with username option Customer reported that some of their krb5 mounts were failing against a single server as the client was trying to mount the shares with wrong credentials. It turned out the client was reusing SMB session from first mount to try mounting the other shares, even though a different username= option had been specified to the other mounts. By using username mount option along with sec=krb5 to search for principals from keytab is supported by cifs.upcall(8) since cifs-utils-4.8. So fix this by matching username mount option in match_session() even with Kerberos. For example, the second mount below should fail with -ENOKEY as there is no 'foobar' principal in keytab (/etc/krb5.keytab). The client ends up reusing SMB session from first mount to perform the second one, which is wrong. ``` $ ktutil ktutil: add_entry -password -p testuser -k 1 -e aes256-cts Password for [email protected]: ktutil: write_kt /etc/krb5.keytab ktutil: quit $ klist -ke Keytab name: FILE:/etc/krb5.keytab KVNO Principal ---- ---------------------------------------------------------------- 1 [email protected] (aes256-cts-hmac-sha1-96) $ mount.cifs //w22-root2/scratch /mnt/1 -o sec=krb5,username=testuser $ mount.cifs //w22-root2/scratch /mnt/2 -o sec=krb5,username=foobar $ mount -t cifs | grep -Po 'username=\K\w+' testuser testuser ```

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.32.44, < 2.6.33>= 2.6.34.12, < 2.6.35>= 2.6.36, < 6.1.167>= 6.2, < 6.6.130>= 6.7, < 6.12.78>= 6.13, < 6.18.20>= 6.19, < 6.19.10= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
Low

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.6.33 / 2.6.35 / 6.1.167 or later
Fixed in 2.6.332.6.356.1.167
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel version 6.6.130 or later (for 6.2+ releases), or 6.1.167 or later (for 6.1.x and earlier affected branches), or the respective fixed minor versions (2.6.33, 2.6.35)

  1. Identify the currently running kernel version using 'uname -r'
  2. Check if the running version falls within any of the affected ranges: >= 2.6.32.44 and < 2.6.33; >= 2.6.34.12 and < 2.6.35; >= 2.6.36 and < 6.1.167; or >= 6.2 and < 6.6.130
  3. If affected, upgrade the kernel to a fixed version: 2.6.33 or later for 2.6.32.x, 2.6.35 or later for 2.6.34.x, 6.1.167 or later for 2.6.36 through 6.1.x, or 6.6.130 or later for 6.2+
  4. After kernel upgrade, reboot the system to load the fixed kernel
  5. Verify the fix by testing Kerberos mount with different username options - each mount with a different username should use separate credentials and not reuse sessions
Caveat Kernel upgrades may require system reboot and could have compatibility implications with proprietary kernel modules or specific hardware drivers; ensure backups and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31392 in production — separate from our analysis above.

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