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smb: client: fix krb5 mount with username option

Type: advisorySource: Official CVE List1 source record

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 ```

Announced Source revision 1
Original source ↗

CVE-2026-31392

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-31392

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "fd4547830720647d4af02ee50f883c4b1cca06e4",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "d33cbf0bf8979d779900da9be2505d68d9d8da25",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "9ee803bfdba0cf739038dbdabdd4c02582c8f2b2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "6e9ff1eb7feedcf46ff2d0503759960ab58e7775",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4ff67b720c02c36e54d55b88c2931879b7db1cd2",
        "lessThan": "12b4c5d98cd7ca46d5035a57bcd995df614c14e1",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "223c7f082d2836ac719b3b228bdcfab35e5e5330",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "88720224330a655ab6268e20109b65b11cfd7f6a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "2.6.32.44",
        "lessThan": "2.6.33",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "2.6.34.12",
        "lessThan": "2.6.35",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/smb/client/connect.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "2.6.36"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "2.6.36",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.1.167",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.130",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.78",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.20",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.10",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/smb/client/connect.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-31392

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#39864 · Revision 1
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Publisher date
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