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Vulnerability Details : CVE-2020-28935

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.
Publish Date : 2020-12-07 Last Update Date : 2021-02-12
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- CVSS Scores & Vulnerability Types

CVSS Score
2.1
Confidentiality Impact None (There is no impact to the confidentiality of the system.)
Integrity Impact None (There is no impact to the integrity of the system)
Availability Impact Partial (There is reduced performance or interruptions in resource availability.)
Access Complexity Low (Specialized access conditions or extenuating circumstances do not exist. Very little knowledge or skill is required to exploit. )
Authentication Not required (Authentication is not required to exploit the vulnerability.)
Gained Access None
Vulnerability Type(s) Denial Of Service
CWE ID 59

- Related OVAL Definitions

Title Definition Id Class Family
RHSA-2021:1853: unbound security, bug fix, and enhancement update (Moderate) oval:com.redhat.rhsa:def:20211853 unix
OVAL (Open Vulnerability and Assessment Language) definitions define exactly what should be done to verify a vulnerability or a missing patch. Check out the OVAL definitions if you want to learn what you should do to verify a vulnerability.

- Products Affected By CVE-2020-28935

# Product Type Vendor Product Version Update Edition Language
1 Application Nlnetlabs Name Server Daemon * * * * Version Details Vulnerabilities
2 Application Nlnetlabs Unbound * * * * Version Details Vulnerabilities

- Number Of Affected Versions By Product

Vendor Product Vulnerable Versions
Nlnetlabs Name Server Daemon 1
Nlnetlabs Unbound 1

- References For CVE-2020-28935

https://www.nlnetlabs.nl/downloads/nsd/CVE-2020-28935.txt CONFIRM
https://www.nlnetlabs.nl/downloads/unbound/CVE-2020-28935.txt CONFIRM
https://security.gentoo.org/glsa/202101-38
GENTOO GLSA-202101-38
https://lists.debian.org/debian-lts-announce/2021/02/msg00017.html
MLIST [debian-lts-announce] 20210212 [SECURITY] [DLA 2556-1] unbound1.9 security update

- Metasploit Modules Related To CVE-2020-28935

There are not any metasploit modules related to this CVE entry (Please visit www.metasploit.com for more information)


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