{
  "threat_severity" : "Low",
  "public_date" : "2020-09-09T00:00:00Z",
  "bugzilla" : {
    "description" : "unbound: symbolic link traversal when writing PID file",
    "id" : "1878761",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1878761"
  },
  "cvss3" : {
    "cvss3_base_score" : "4.4",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N",
    "status" : "verified"
  },
  "cwe" : "CWE-59",
  "details" : [ "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.", "A symbolic link traversal vulnerability was found in unbound in the way it writes its PID file while starting up. This flaw allows a local attacker with access to the unbound user to set up a link to another file, owned by root, and make unbound overwrite it during its next restart, destroying the original content. The highest threat from this vulnerability is integrity." ],
  "acknowledgement" : "This issue was discovered by Mason Loring Bliss (Red Hat).",
  "affected_release" : [ {
    "product_name" : "Red Hat Enterprise Linux 8",
    "release_date" : "2021-05-18T00:00:00Z",
    "advisory" : "RHSA-2021:1853",
    "cpe" : "cpe:/a:redhat:enterprise_linux:8",
    "package" : "unbound-0:1.7.3-15.el8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8.2 Extended Update Support",
    "release_date" : "2022-02-22T00:00:00Z",
    "advisory" : "RHSA-2022:0632",
    "cpe" : "cpe:/a:redhat:rhel_eus:8.2",
    "package" : "unbound-0:1.7.3-12.el8_2"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Out of support scope",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Out of support scope",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2020-28935\nhttps://nvd.nist.gov/vuln/detail/CVE-2020-28935" ],
  "name" : "CVE-2020-28935",
  "mitigation" : {
    "value" : "If SELinux is enabled in Enforcing mode (the default value in Red Hat Enterprise Linux 8), this kind of attack is prevented as unbound would be blocked from accessing the symbolic link file.",
    "lang" : "en:us"
  },
  "csaw" : false
}