CVE Intelligence
High

CVE-2026-31392 — smb: client: fix krb5 mount with username option

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 testuser@ZELDA.TEST: ktutil: write_kt /etc/krb5.keytab ktutil: quit $ klist -ke Keytab name: FILE:/etc/krb5.keytab KVNO Principal ---- ---------------------------------------------------------------- 1 testuser@ZELDA.TEST (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 ```

Published Apr 3, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.2% (30-day exploitation probability)+1
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.18%
ahead of 7% of scored CVEs · Oct 14, 2026
Affects
Linux
Linux and 1 more
CVSS base
8.1
High · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Linux Linux ≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < fd4547830720647d4af02ee50f883c4b1cca06e4version 2.6.36≥ 2.6.34.12 and < 2.6.35≥ 2.6.32.44 and < 2.6.33version 88720224330a655ab6268e20109b65b11cfd7f6aversion 223c7f082d2836ac719b3b228bdcfab35e5e5330≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < 12b4c5d98cd7ca46d5035a57bcd995df614c14e1≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < 6e9ff1eb7feedcf46ff2d0503759960ab58e7775
and 3 more ≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < 9ee803bfdba0cf739038dbdabdd4c02582c8f2b2≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < d33cbf0bf8979d779900da9be2505d68d9d8da25≥ 4ff67b720c02c36e54d55b88c2931879b7db1cd2 and < 9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2
Vulnerable CVE Program (cve.org) e CISA ADP
Linux Linux Kernel ≥ 2.6.32.44 and < 2.6.33version 7.0-rc4version 7.0-rc3version 7.0-rc2version 7.0-rc1≥ 6.19 and < 6.19.10≥ 6.13 and < 6.18.20≥ 6.7 and < 6.12.78
and 3 more ≥ 6.2 and < 6.6.130≥ 2.6.36 and < 6.1.167≥ 2.6.34.12 and < 2.6.35
Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
Low

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.1 CVSS 3.1 High 1.5 6.0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
8.1 CVSS 3.1 High — — Linux via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.18%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · linux/linux
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 8.1
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Apr 3, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

6 on the record

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

  • CVE-2026-99999 ipv4: validate checksum_start before completing checksum 9h
  • CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 9h
  • CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
  • CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
  • CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
  • CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No CISA SSVC assessment.
  • No CWE classification.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-31392 is "smb: client: fix krb5 mount with username option", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 0.18% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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