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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities
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CVE-2020-28935 Detail

Description

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.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://lists.debian.org/debian-lts-announce/2021/02/msg00017.html Mailing List  Third Party Advisory 
https://lists.debian.org/debian-lts-announce/2023/03/msg00024.html
https://security.gentoo.org/glsa/202101-38 Third Party Advisory 
https://www.nlnetlabs.nl/downloads/nsd/CVE-2020-28935.txt Vendor Advisory 
https://www.nlnetlabs.nl/downloads/unbound/CVE-2020-28935.txt Vendor Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-59 Improper Link Resolution Before File Access ('Link Following') cwe source acceptance level NIST   NLnet Labs  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

7 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2020-28935
NVD Published Date:
12/07/2020
NVD Last Modified:
03/29/2023
Source:
NLnet Labs