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Avahi CVE-2026-34933

MEDIUM
Reachable Assertion (CWE-617)
2026-04-03 GitHub_M
Denial Of Service Avahi
5.5
CVSS 3.1 · Vendor: GitHub_M
View

Vulnerability Assessment

Weakness
CWE
CWE-617
ASVS 5.0
V16 - Security Logging and Error Handling Reachable assertion handling
Impact

CVSS score of 5.5 with vector AV:L/AC:L/PR:L/UI:N/S:U indicates a local attack requiring low privileges and low complexity, with high availability impact but no confidentiality or integrity impact. EPSS and KEV status are not provided in the input data. While the CVSS score is moderate, the real-world risk is contextual: any system where local unprivileged users can access the D-Bus service (typical on multi-user systems or containerized environments) faces practical denial-of-service risk. The low attack complexity and lack of user interaction requirements make this operationally feasible. However, impact is limited to availability-no data exfiltration or privilege escalation is possible. For single-user systems or those with restricted D-Bus access, risk is lower. This is a legitimate but bounded denial-of-service issue rather than a critical vulnerability.
Exploit ScenarioDerived

An unprivileged local user on a multi-user system sends a specially crafted D-Bus method call to avahi-daemon with conflicting publish flags (e.g., attempting to publish a service with mutually exclusive attributes). The daemon's input validation fails to catch the conflict, triggering an assertion failure that immediately crashes the avahi-daemon process. This causes all mDNS/DNS-SD service discovery to cease until the daemon is restarted, affecting local network service discovery for all users. No specialized tools are required-a simple D-Bus call using standard tools (e.g., dbus-send) suffices.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Apr 03, 2026

Denial of service in Avahi prior to version 0.9-rc4 allows local unprivileged users to crash avahi-daemon by sending a D-Bus method call with conflicting publish flags. The vulnerability requires local access and low privileges but causes immediate service unavailability. No public exploit code or active exploitation has been confirmed; however, the attack is trivial to execute given the low complexity barrier.

RemediationAI

Vendor-released patch: Avahi 0.9-rc4 and later versions contain the fix. Users should upgrade avahi-daemon to version 0.9-rc4 or a later stable release when available. The upstream fix is documented in GitHub PR #891 and commit 625ca0fac19229f6dfa3a6c6b698ae657187e50c. Until patching is possible, restrict D-Bus method call access to avahi-daemon to trusted users via D-Bus policy configuration, though this may impact legitimate service discovery functionality. See the security advisory at https://github.com/avahi/avahi/security/advisories/GHSA-w65r-6gxh-vhvc for complete details.

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Technical ContextAI · show details

Avahi is a mDNS/DNS-SD service discovery daemon commonly deployed on Linux systems. The vulnerability exists in the D-Bus interface exposed by avahi-daemon, which processes service publication requests. The root cause is classified as CWE-617 (Reachable Assertion), indicating that the daemon fails to properly validate conflicting publish flag combinations before processing them, resulting in an unhandled assertion or crash. The affected product spans all Avahi versions prior to 0.9-rc4, as identified by CPE cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*.

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Severity by source

Vendor (GitHub_M) PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SUSE MEDIUM
Red Hat 5.5 MEDIUM

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

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

DescriptionCVE.org

Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. Prior to version 0.9-rc4, any unprivileged local user can crash avahi-daemon by sending a single D-Bus method call with conflicting publish flags. This issue has been patched in version 0.9-rc4.

Threat Intelligence Overview

EPSS Score
0.0%
Top 98% exploitable
Social Media
1
Sightings
Data Quality
7 sources
Confidence: High
NVD CVE.org EPSS Vulnrichment Vendor CIRCL GitHub VulDB

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 0.0%
Patch available Yes
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
Scheduled
Exploitation
Poc
System Exposure· derived
Small
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

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)CVE.org

cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*

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Avahi daemon versions 0.9rc2 and below can be remotely crashed through a denial of service attack by sending a specially
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Same weakness CWE-617 – Reachable Assertion

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CVE-2020-12417 HIGH POC
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CVE-2020-6619 HIGH POC
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Same technique Denial Of Service

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CVE-2015-5119 CRITICAL POC
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CVE-2011-2462 CRITICAL POC
9.8
CVE-2011-0611 HIGH POC
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CVE-2012-1889 HIGH POC
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CVE-2012-0507 CRITICAL POC
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CVE-2014-1761 HIGH POC
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CVE-2015-5122 CRITICAL POC
9.8
CVE-2011-0609 HIGH POC
7.8

Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Micro 5.2 Fixed
SUSE Linux Enterprise Micro 5.3 Fixed
SUSE Linux Enterprise Micro 5.4 Fixed

References

Advisories & patches
ADVISORY https://ubuntu.com/security/notices/USN-8269-1 ADVISORY https://vuldb.com/vuln/355258 REF http://www.openwall.com/lists/oss-security/2026/04/11/9 REF https://github.com/avahi/avahi/commit/625ca0fac19229f6dfa3a6c6b698ae657187e50c REF https://github.com/avahi/avahi/pull/891 REF https://github.com/avahi/avahi/security/advisories/GHSA-w65r-6gxh-vhvc

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