Vulnerability Details : CVE-2021-26720
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.
Vulnerability category: Denial of service
Products affected by CVE-2021-26720
- cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
- cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-26720
0.04%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 10 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-26720
| Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
|---|---|---|---|---|---|---|
|
4.6
|
MEDIUM | AV:L/AC:L/Au:N/C:P/I:P/A:P |
3.9
|
6.4
|
NIST | |
|
7.8
|
HIGH | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
1.8
|
5.9
|
NIST |
CWE ids for CVE-2021-26720
-
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-26720
-
https://packages.debian.org/bullseye/avahi-daemon
Debian -- Details of package avahi-daemon in bullseyeProduct;Third Party Advisory
-
https://bugzilla.suse.com/show_bug.cgi?id=1180827
Bug 1180827 – VUL-0: CVE-2021-26720: avahi: outdated and insecure if-up script avahi-daemon-check-dns.shIssue Tracking;Third Party Advisory
-
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796
#982796 - buster-pu: package avahi/0.7-4 - Debian Bug report logsMailing List;Third Party Advisory
-
https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog
404 Not FoundBroken Link;Third Party Advisory
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https://security-tracker.debian.org/tracker/CVE-2021-26720
CVE-2021-26720Third Party Advisory
-
https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html
[SECURITY] [DLA 3047-1] avahi security updateMailing List;Third Party Advisory
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https://packages.debian.org/buster/avahi-daemon
Debian -- Details of package avahi-daemon in busterProduct;Third Party Advisory
-
https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824
Bug #1870824 “Errors in script /usr/lib/avahi/avahi-daemon-check...” : Bugs : avahi package : UbuntuIssue Tracking;Third Party Advisory
-
https://www.openwall.com/lists/oss-security/2021/02/15/2
oss-security - CVE-2021-26720: avahi-daemon: 'avahi' to 'root' user privilege escalation through Debian specific if-up script avahi-daemon-check-dns.shMailing List;Third Party Advisory
-
https://packages.debian.org/sid/avahi-daemon
Debian -- Details of package avahi-daemon in sidProduct;Third Party Advisory
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