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Avahi CVE-2021-3468

MEDIUM
Loop with Unreachable Exit Condition (Infinite Loop) (CWE-835)
2021-06-02 secalert@redhat.com
Denial Of Service Debian Avahi Debian Linux
5.5
CVSS 3.1 · NVD
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Vulnerability Assessment

Weakness
CWE
CWE-835
ASVS 5.0
V15 - Secure Coding and Architecture Loop termination conditions
MITRE ATT&CK

1 technique across 1 tactic: Impact

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS score of 5.5 (MEDIUM). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required.
Exploit ScenarioDerived

Successful exploitation could compromise the medium-severity affected system.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.5% exploitation probability (EPSS)

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AnalysisAI

A flaw was found in avahi in versions 0.6 up to 0.8. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-835. A flaw was found in avahi in versions 0.6 up to 0.8. The event used to signal the termination of the client connection on the avahi Unix socket is not correctly handled in the client_work function, allowing a local attacker to trigger an infinite loop. The highest threat from this vulnerability is to the availability of the avahi service, which becomes unresponsive after this flaw is triggered. Affected products include: Avahi, Debian Debian Linux. Version information: up to 0.8..

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

DescriptionNVD

A flaw was found in avahi in versions 0.6 up to 0.8. The event used to signal the termination of the client connection on the avahi Unix socket is not correctly handled in the client_work function, allowing a local attacker to trigger an infinite loop. The highest threat from this vulnerability is to the availability of the avahi service, which becomes unresponsive after this flaw is triggered.

Threat Intelligence Overview

EPSS Score
0.5%
Top 64% exploitable
Data Quality
2 sources
Confidence: Low
NVD CVE.org EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.5%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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A flaw was found in avahi 0.8-5. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. Public e
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Same weakness CWE-835 – Loop with Unreachable Exit Condition (Infinite Loop)

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References

Advisories & patches
REF https://bugzilla.redhat.com/show_bug.cgi?id=1939614 REF https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html REF https://lists.debian.org/debian-lts-announce/2023/06/msg00028.html

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