CVE-2021-26720 - Improper Link Resolution Before File Access ('Link Following')

Severity

78%

Complexity

18%

Confidentiality

98%

avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon, and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE), not the upstream Avahi product.

CVSS 3.1 Base Score 7.8. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

CVSS 2.0 Base Score 4.6. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (AV:L/AC:L/Au:N/C:P/I:P/A:P).

Overview

First reported 4 years ago

2021-02-17 22:15:00

Last updated 3 years ago

2021-02-25 21:27:00

Affected Software

Debian Linux 9.0

9.0

References

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796

https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824

https://bugzilla.suse.com/show_bug.cgi?id=1180827

https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog

https://packages.debian.org/bullseye/avahi-daemon

https://packages.debian.org/buster/avahi-daemon

https://packages.debian.org/sid/avahi-daemon

https://security-tracker.debian.org/tracker/CVE-2021-26720

https://www.openwall.com/lists/oss-security/2021/02/15/2

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796

Mailing List, Third Party Advisory

https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824

Issue Tracking, Third Party Advisory

https://bugzilla.suse.com/show_bug.cgi?id=1180827

Issue Tracking, Third Party Advisory

https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog

Broken Link, Third Party Advisory

https://packages.debian.org/bullseye/avahi-daemon

Product, Third Party Advisory

https://packages.debian.org/buster/avahi-daemon

Product, Third Party Advisory

https://packages.debian.org/sid/avahi-daemon

Product, Third Party Advisory

https://security-tracker.debian.org/tracker/CVE-2021-26720

Third Party Advisory

https://www.openwall.com/lists/oss-security/2021/02/15/2

Mailing List, Third Party Advisory

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