FKIE_CVE-2026-31392

Vulnerability from fkie_nvd - Published: 2026-04-03 16:16 - Updated: 2026-07-21 19:10
Severity
8.1 (High) - CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L
Summary
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 ```
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/12b4c5d98cd7ca46d5035a57bcd995df614c14e1Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6e9ff1eb7feedcf46ff2d0503759960ab58e7775Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9ee803bfdba0cf739038dbdabdd4c02582c8f2b2Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d33cbf0bf8979d779900da9be2505d68d9d8da25Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fd4547830720647d4af02ee50f883c4b1cca06e4Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
To clipboard 

{
  "affected": [
    {
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          "product": "Linux",
          "programFiles": [
            "fs/smb/client/connect.c"
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
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              "status": "unaffected",
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              "versionType": "semver"
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              "status": "unaffected",
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              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.10",
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
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  "configurations": [
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          "negate": false,
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix krb5 mount with username option\n\nCustomer reported that some of their krb5 mounts were failing against\na single server as the client was trying to mount the shares with\nwrong credentials.  It turned out the client was reusing SMB session\nfrom first mount to try mounting the other shares, even though a\ndifferent username= option had been specified to the other mounts.\n\nBy using username mount option along with sec=krb5 to search for\nprincipals from keytab is supported by cifs.upcall(8) since\ncifs-utils-4.8.  So fix this by matching username mount option in\nmatch_session() even with Kerberos.\n\nFor example, the second mount below should fail with -ENOKEY as there\nis no \u0027foobar\u0027 principal in keytab (/etc/krb5.keytab).  The client\nends up reusing SMB session from first mount to perform the second\none, which is wrong.\n\n```\n$ ktutil\nktutil:  add_entry -password -p testuser -k 1 -e aes256-cts\nPassword for testuser@ZELDA.TEST:\nktutil:  write_kt /etc/krb5.keytab\nktutil:  quit\n$ klist -ke\nKeytab name: FILE:/etc/krb5.keytab\nKVNO Principal\n ---- ----------------------------------------------------------------\n   1 testuser@ZELDA.TEST (aes256-cts-hmac-sha1-96)\n$ mount.cifs //w22-root2/scratch /mnt/1 -o sec=krb5,username=testuser\n$ mount.cifs //w22-root2/scratch /mnt/2 -o sec=krb5,username=foobar\n$ mount -t cifs | grep -Po \u0027username=\\K\\w+\u0027\ntestuser\ntestuser\n```"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nsmb: cliente: corregir montaje krb5 con opci\u00f3n de nombre de usuario\n\nEl cliente inform\u00f3 que algunos de sus montajes krb5 estaban fallando contra un \u00fanico servidor ya que el cliente estaba intentando montar los recursos compartidos con credenciales incorrectas. Result\u00f3 que el cliente estaba reutilizando la sesi\u00f3n SMB del primer montaje para intentar montar los otros recursos compartidos, a pesar de que una opci\u00f3n diferente de username= hab\u00eda sido especificada para los otros montajes.\n\nEl uso de la opci\u00f3n de montaje de nombre de usuario junto con sec=krb5 para buscar principales de keytab es compatible con cifs.upcall(8) desde cifs-utils-4.8. Por lo tanto, corrija esto al hacer coincidir la opci\u00f3n de montaje de nombre de usuario en match_session() incluso con Kerberos.\n\nPor ejemplo, el segundo montaje a continuaci\u00f3n deber\u00eda fallar con -ENOKEY ya que no hay ning\u00fan principal  foobar  en keytab (/etc/krb5.keytab). El cliente termina reutilizando la sesi\u00f3n SMB del primer montaje para realizar el segundo, lo cual es incorrecto.\n\n\u0027\u0027\u0027\n$ ktutil\nktutil:  add_entry -password -p testuser -k 1 -e aes256-cts\nPassword for testuser@ZELDA.TEST:\nktutil:  write_kt /etc/krb5.keytab\nktutil:  quit\n$ klist -ke\nKeytab name: FILE:/etc/krb5.keytab\nKVNO Principal\n ---- ----------------------------------------------------------------\n   1 testuser@ZELDA.TEST (aes256-cts-hmac-sha1-96)\n$ mount.cifs //w22-root2/scratch /mnt/1 -o sec=krb5,username=testuser\n$ mount.cifs //w22-root2/scratch /mnt/2 -o sec=krb5,username=foobar\n$ mount -t cifs | grep -Po  username=\\K\\w+ \ntestuser\ntestuser\n\u0027\u0027\u0027"
    }
  ],
  "id": "CVE-2026-31392",
  "lastModified": "2026-07-21T19:10:00.107",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "LOW",
          "baseScore": 8.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "HIGH",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 1.5,
        "impactScore": 6.0,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-04-03T16:16:37.300",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/12b4c5d98cd7ca46d5035a57bcd995df614c14e1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/6e9ff1eb7feedcf46ff2d0503759960ab58e7775"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "url": "https://git.kernel.org/stable/c/9229709ec8bf85ae7ca53aeee9aa14814cdc1bd2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/9ee803bfdba0cf739038dbdabdd4c02582c8f2b2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/d33cbf0bf8979d779900da9be2505d68d9d8da25"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/fd4547830720647d4af02ee50f883c4b1cca06e4"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}



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