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CVE-2021-3502

19
FAUCET Score

CVE-2021-3502 is a medium-severity vulnerability affecting Avahi 0.8-5, where a local attacker can crash the Avahi service by requesting hostname resolutions for invalid hostnames. This flaw, a reachable assertion in the avahi_s_host_name_resolver_start function, primarily impacts service availability. The vulnerability has a CVSS score of 5.5, indicating a local attack vector with low complexity and high impact on availability. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage, suggesting a low current threat profile.

Impacted Technologies

VendorProductVersion(s)CPE
0.8-5CPE matchmatch criteria
cpe:2.3:a:avahi:avahi:0.8-5:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.37%
Probability of exploitation in next 30 days
EPSS Percentile
30.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0037 is in the 86th percentile among its peer group of 15,940 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (8)

microsoftpatch availablevia msrc
Product: Azure Linux 3.0 ARMFixed in: 0.8-1
microsoftpatch availablevia msrc
Product: 17556-17084Fixed in: 0.8-1
microsoftpatch availablevia msrc
Product: 19075-17084Fixed in: 0.8-1
microsoftpatch availablevia msrc
Product: azl3 avahi 0.8-1 on Azure Linux 3.0Fixed in: 0.8-1
microsoftpatch availablevia msrc
Product: Azure Linux 3.0 x64Fixed in: 0.8-1
microsoftpatch availablevia msrc
Product: azl3 avahi 0.8-5 on Azure Linux 3.0Fixed in: 0.8-1
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: avahi-0:0.8-15.el9
View patch
redhatpatch availablevia nvd_reference
View patch

Vendor Advisories (3)

microsoft2024-Jun/CVE-2021-3502

CVE-2021-3502

Jun 11, 2024
microsoft2021-May/CVE-2021-3502Moderate

A flaw was found in avahi 0.8-5. A reachable assertion is present in avahi_s_host_name_resolver_start function allowing a local attacker to crash the avahi service by requesting hostname resolutions through the avahi socket or dbus methods for invalid hostnames. The highest threat from this vulnerability is to the service availability.

May 11, 2021
redhatCVE-2021-3502Moderate

avahi: reachable assertion in avahi_s_host_name_resolver_start when trying to resolve badly-formatted hostnames

Mar 29, 2021

References

bugzilla.redhat.com / show_bug.cgi
ExploitIssue TrackingPatchThird Party Advisory
github.com / lathiat/avahi/issues/338
ExploitThird Party Advisory