CVE-2026-31392smb: client: fix krb5 mount with username option
- 8.1HighCVSS base score
- 0.12%Exploitation in 30 daysEPSS · top 98% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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 ```
Timeline
ID reserved
By Linux
- 25 days later
· 25 days later
Published
- 7 months later
· 7 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High8.1 | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L |
| NVDNVD · Modified | 3.1 | High8.1 | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L |
- EPSS (exploitation in 30 days)
- 0.12% · top 98% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.1.
Affected products
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < fd4547830720647d4af02ee50f883c4b1cca06e4
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < 9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < d33cbf0bf8979d779900da9be2505d68d9d8da25
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < 9ee803bfdba0cf739038dbdabdd4c02582c8f2b2
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < 6e9ff1eb7feedcf46ff2d0503759960ab58e7775
- affected 4ff67b720c02c36e54d55b88c2931879b7db1cd2 – < 12b4c5d98cd7ca46d5035a57bcd995df614c14e1
- affected 223c7f082d2836ac719b3b228bdcfab35e5e5330
- affected 88720224330a655ab6268e20109b65b11cfd7f6a
- affected 2.6.32.44 – < 2.6.33
- affected 2.6.34.12 – < 2.6.35
- affected 2.6.36
- unaffected < 2.6.36
- unaffected 6.1.167 – ≤ 6.1.*
- unaffected 6.6.130 – ≤ 6.6.*
- unaffected 6.12.78 – ≤ 6.12.*
- unaffected 6.18.20 – ≤ 6.18.*
- unaffected 6.19.10 – ≤ 6.19.*
- unaffected 7.0 – ≤ *
References
References6
- https://git.kernel.org/stable/c/fd4547830720647d4af02ee50f883c4b1cca06e4 (opens in a new tab)
- https://git.kernel.org/stable/c/9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2 (opens in a new tab)
- https://git.kernel.org/stable/c/d33cbf0bf8979d779900da9be2505d68d9d8da25 (opens in a new tab)
- https://git.kernel.org/stable/c/9ee803bfdba0cf739038dbdabdd4c02582c8f2b2 (opens in a new tab)
- https://git.kernel.org/stable/c/6e9ff1eb7feedcf46ff2d0503759960ab58e7775 (opens in a new tab)
- https://git.kernel.org/stable/c/12b4c5d98cd7ca46d5035a57bcd995df614c14e1 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-18766 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-31392)Record last updated .