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Arch Linux Advisory ASA-202012-18 Low: nsd Denial Of Service Issue

The package nsd before version 4.3.4-1 is vulnerable to denial of service. . Arch Linux Security Advisory ASA-202012-18 ========================================= Severity: Low Date : 2020-12-09 CVE-ID : CVE-2020-28935 Package : nsd Type : denial of service Remote : No Link : https://security.archlinux.org/AVG-1327 Summary ====== The package nsd before version 4.3.4-1 is vulnerable to denial of service. Resolution ========= Upgrade to 4.3.4-1. # pacman -Syu "nsd> =4.3.4-1" The problem has been fixed upstream in version 4.3.4. Workaround ========= None. 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. Impact ===== A local attacker might be able to cause a denial of service ofthe host. References ========= https://www.nlnetlabs.nl/downloads/unbound/CVE-2020-28935.txt https://github.com/NLnetLabs/unbound/issues/303 https://nlnetlabs.nl/downloads/unbound/patch_cve-2020-28935_unbound.diff https://github.com/NLnetLabs/unbound/commit/ad387832979b6ce4c93f64fe706301cd7d034e87 https://github.com/NLnetLabs/unbound/commit/19f8f4d9f99a44906ab9dcc46d44da299fde3506 https://nlnetlabs.nl/downloads/nsd/patch_cve-2020-28935_nsd.diff https://github.com/NLnetLabs/nsd/commit/a4caec3137a1bc9eca05d38d66e2bce572ca9bd3 https://security.archlinux.org/CVE-2020-28935 . Arch Linux Alert regarding the bind package: service disruption vulnerability addressed in release 9.11.6-2.. Arch Linux, nsd package, denial of service. . Severity: Low. LinuxSecurity.com Team

Dec 17, 2020 •Low ArchLinux