fkie_cve-2020-28935
Vulnerability from fkie_nvd
Published
2020-12-07 22:15
Modified
2024-11-21 05:23
Summary
NLnet Labs Unbound, up to and including version 1.12.0, and NLnet Labs NSD, up to and including version 4.3.3, contain a local vulnerability that would allow for a local symlink attack. When writing the PID file, Unbound and NSD create the file if it is not there, or open an existing file for writing. In case the file was already present, they would follow symlinks if the file happened to be a symlink instead of a regular file. An additional chown of the file would then take place after it was written, making the user Unbound/NSD is supposed to run as the new owner of the file. If an attacker has local access to the user Unbound/NSD runs as, she could create a symlink in place of the PID file pointing to a file that she would like to erase. If then Unbound/NSD is killed and the PID file is not cleared, upon restarting with root privileges, Unbound/NSD will rewrite any file pointed at by the symlink. This is a local vulnerability that could create a Denial of Service of the system Unbound/NSD is running on. It requires an attacker having access to the limited permission user Unbound/NSD runs as and point through the symlink to a critical file on the system.
Impacted products



{
   configurations: [
      {
         nodes: [
            {
               cpeMatch: [
                  {
                     criteria: "cpe:2.3:a:nlnetlabs:name_server_daemon:*:*:*:*:*:*:*:*",
                     matchCriteriaId: "2999AD3A-4E86-4E7F-94DC-7972AF046056",
                     versionEndExcluding: "4.3.4",
                     vulnerable: true,
                  },
                  {
                     criteria: "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
                     matchCriteriaId: "B5033957-63F8-4F49-A451-96BEF9644520",
                     versionEndExcluding: "1.13.0",
                     vulnerable: true,
                  },
               ],
               negate: false,
               operator: "OR",
            },
         ],
      },
      {
         nodes: [
            {
               cpeMatch: [
                  {
                     criteria: "cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*",
                     matchCriteriaId: "DEECE5FC-CACF-4496-A3E7-164736409252",
                     vulnerable: true,
                  },
               ],
               negate: false,
               operator: "OR",
            },
         ],
      },
   ],
   cveTags: [],
   descriptions: [
      {
         lang: "en",
         value: "NLnet Labs Unbound, up to and including version 1.12.0, and NLnet Labs NSD, up to and including version 4.3.3, contain a local vulnerability that would allow for a local symlink attack. When writing the PID file, Unbound and NSD create the file if it is not there, or open an existing file for writing. In case the file was already present, they would follow symlinks if the file happened to be a symlink instead of a regular file. An additional chown of the file would then take place after it was written, making the user Unbound/NSD is supposed to run as the new owner of the file. If an attacker has local access to the user Unbound/NSD runs as, she could create a symlink in place of the PID file pointing to a file that she would like to erase. If then Unbound/NSD is killed and the PID file is not cleared, upon restarting with root privileges, Unbound/NSD will rewrite any file pointed at by the symlink. This is a local vulnerability that could create a Denial of Service of the system Unbound/NSD is running on. It requires an attacker having access to the limited permission user Unbound/NSD runs as and point through the symlink to a critical file on the system.",
      },
      {
         lang: "es",
         value: "NLnet Labs Unbound, hasta la versión 1.12.0 incluyéndola, y NLnet Labs NSD, hasta la versión 4.3.3 incluyéndola, contienen una vulnerabilidad local que permitiría un ataque de tipo symlink local. Al escribir el archivo PID, Unbound y NSD crean el archivo si no está allí, o abren un archivo existente para escribir. En caso de que el archivo ya existiera, seguirían enlaces simbólicos si el archivo fuera un enlace simbólico en lugar de un archivo normal. Luego, se llevaría a cabo una copia adicional del archivo después de que se escribió, lo que haría que el usuario Unbound/NSD se ejecute como el nuevo propietario del archivo. Si un atacante tiene acceso local al usuario con el que se ejecuta Unbound/NSD, podría crear un enlace simbólico en lugar del archivo PID que apunta hacia un archivo que le gustaría borrar. Si luego Unbound/NSD es eliminado y el archivo PID no se borra, al reiniciar con privilegios root, Unbound/NSD reescribirá cualquier archivo apuntado por el enlace simbólico. Esta es una vulnerabilidad local que podría crear una Denegación de Servicio del sistema en el que se ejecuta Unbound/NSD. Requiere que un atacante tenga acceso al usuario de permiso limitado que se ejecuta como Unbound/NSD y apunta por medio del enlace simbólico a un archivo crítico en el sistema",
      },
   ],
   id: "CVE-2020-28935",
   lastModified: "2024-11-21T05:23:19.620",
   metrics: {
      cvssMetricV2: [
         {
            acInsufInfo: false,
            baseSeverity: "LOW",
            cvssData: {
               accessComplexity: "LOW",
               accessVector: "LOCAL",
               authentication: "NONE",
               availabilityImpact: "PARTIAL",
               baseScore: 2.1,
               confidentialityImpact: "NONE",
               integrityImpact: "NONE",
               vectorString: "AV:L/AC:L/Au:N/C:N/I:N/A:P",
               version: "2.0",
            },
            exploitabilityScore: 3.9,
            impactScore: 2.9,
            obtainAllPrivilege: false,
            obtainOtherPrivilege: false,
            obtainUserPrivilege: false,
            source: "nvd@nist.gov",
            type: "Primary",
            userInteractionRequired: false,
         },
      ],
      cvssMetricV31: [
         {
            cvssData: {
               attackComplexity: "LOW",
               attackVector: "LOCAL",
               availabilityImpact: "HIGH",
               baseScore: 5.5,
               baseSeverity: "MEDIUM",
               confidentialityImpact: "NONE",
               integrityImpact: "NONE",
               privilegesRequired: "LOW",
               scope: "UNCHANGED",
               userInteraction: "NONE",
               vectorString: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
               version: "3.1",
            },
            exploitabilityScore: 1.8,
            impactScore: 3.6,
            source: "nvd@nist.gov",
            type: "Primary",
         },
      ],
   },
   published: "2020-12-07T22:15:20.853",
   references: [
      {
         source: "sep@nlnetlabs.nl",
         tags: [
            "Mailing List",
            "Third Party Advisory",
         ],
         url: "https://lists.debian.org/debian-lts-announce/2021/02/msg00017.html",
      },
      {
         source: "sep@nlnetlabs.nl",
         url: "https://lists.debian.org/debian-lts-announce/2023/03/msg00024.html",
      },
      {
         source: "sep@nlnetlabs.nl",
         tags: [
            "Third Party Advisory",
         ],
         url: "https://security.gentoo.org/glsa/202101-38",
      },
      {
         source: "sep@nlnetlabs.nl",
         tags: [
            "Vendor Advisory",
         ],
         url: "https://www.nlnetlabs.nl/downloads/nsd/CVE-2020-28935.txt",
      },
      {
         source: "sep@nlnetlabs.nl",
         tags: [
            "Vendor Advisory",
         ],
         url: "https://www.nlnetlabs.nl/downloads/unbound/CVE-2020-28935.txt",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Mailing List",
            "Third Party Advisory",
         ],
         url: "https://lists.debian.org/debian-lts-announce/2021/02/msg00017.html",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         url: "https://lists.debian.org/debian-lts-announce/2023/03/msg00024.html",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Third Party Advisory",
         ],
         url: "https://security.gentoo.org/glsa/202101-38",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Vendor Advisory",
         ],
         url: "https://www.nlnetlabs.nl/downloads/nsd/CVE-2020-28935.txt",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Vendor Advisory",
         ],
         url: "https://www.nlnetlabs.nl/downloads/unbound/CVE-2020-28935.txt",
      },
   ],
   sourceIdentifier: "sep@nlnetlabs.nl",
   vulnStatus: "Modified",
   weaknesses: [
      {
         description: [
            {
               lang: "en",
               value: "CWE-59",
            },
         ],
         source: "sep@nlnetlabs.nl",
         type: "Secondary",
      },
      {
         description: [
            {
               lang: "en",
               value: "CWE-59",
            },
         ],
         source: "nvd@nist.gov",
         type: "Primary",
      },
   ],
}


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