Upstream information

CVE-2020-28935 at MITRE


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.

SUSE information

Overall state of this security issue: Pending

This issue is currently rated as having moderate severity.

CVSS v2 Scores
  National Vulnerability Database
Base Score 2.1
Vector AV:L/AC:L/Au:N/C:N/I:N/A:P
Access Vector Local
Access Complexity Low
Authentication None
Confidentiality Impact None
Integrity Impact None
Availability Impact Partial
CVSS v3 Scores
  National Vulnerability Database SUSE
Base Score 5.5 4.4
Access Vector Local Local
Access Complexity Low Low
Privileges Required Low High
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact None None
Integrity Impact None High
Availability Impact High None
CVSSv3 Version 3.1 3.1
SUSE Bugzilla entries: 1173619 [NEW], 1179191 [RESOLVED / FIXED]

SUSE Security Advisories:

List of released packages

Product(s) Fixed package version(s) References
SUSE Package Hub for SUSE Linux Enterprise 12
  • nsd >= 4.3.4-8.1
SUSE Package Hub for SUSE Linux Enterprise 15 SP1
  • nsd >= 4.1.27-bp151.3.3.1
SUSE Package Hub for SUSE Linux Enterprise 15 SP2
  • nsd >= 4.3.4-bp152.2.3.1
openSUSE Leap 15.1
  • nsd >= 4.1.27-lp151.2.3.1
openSUSE Leap 15.2
  • nsd >= 4.3.4-lp152.2.3.1
openSUSE Tumbleweed
  • libunbound8 >= 1.13.2-1.2
  • nsd >= 4.3.7-1.2
  • python3-unbound >= 1.13.2-1.2
  • unbound >= 1.13.2-1.2
  • unbound-anchor >= 1.13.2-1.2
  • unbound-devel >= 1.13.2-1.2
  • unbound-munin >= 1.13.2-1.2
openSUSE Tumbleweed GA libunbound8-1.13.2-1.2
openSUSE Tumbleweed GA nsd-4.3.7-1.2

Status of this issue by product and package

Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification.

Product(s) Source package State
SUSE Linux Enterprise High Performance Computing 15 LTSS unbound Affected
SUSE Linux Enterprise Module for Basesystem 15 SP1 unbound Affected
SUSE Linux Enterprise Module for Basesystem 15 SP2 unbound Affected
SUSE Linux Enterprise Server 15 LTSS unbound Affected
SUSE Linux Enterprise Server ESPOS 15 unbound Affected
SUSE Linux Enterprise Server for SAP Applications 15 unbound Affected