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Full vulnerability report · 2026
CVE-2026-34933High confidence

Avahi: Reachable assertion in `transport_flags_from_domain()` via conflicting publish flags crashes avahi-daemon

avahi · avahi

Official source article: GitHub GHSA-W65R-6GXH-VHVC ↗. Check the applicable product and release in the original source.

5.5MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 0.16% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs avahi avahi and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 4 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourceavahiAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourceavahiAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourceavahiAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourceavahiAffected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archiveavahiVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.0.8-13ubuntu6.2Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-34933 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityavahi: avahi-daemon: Avahi: Denial of Service via D-Bus method call
90 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • avahi as a component of Red Hat Enterprise Linux 10
  • avahi-compat-howl as a component of Red Hat Enterprise Linux 10
  • avahi-compat-howl-devel as a component of Red Hat Enterprise Linux 10
  • avahi-compat-libdns_sd as a component of Red Hat Enterprise Linux 10
  • avahi-compat-libdns_sd-devel as a component of Red Hat Enterprise Linux 10
  • avahi-devel as a component of Red Hat Enterprise Linux 10
  • avahi-glib as a component of Red Hat Enterprise Linux 10
  • avahi-glib-devel as a component of Red Hat Enterprise Linux 10
  • avahi-libs as a component of Red Hat Enterprise Linux 10
  • avahi-tools as a component of Red Hat Enterprise Linux 10
  • avahi.src as a component of Red Hat Enterprise Linux 10
  • avahi as a component of Red Hat Enterprise Linux 6
Summary
A flaw was found in Avahi. An unprivileged local user can exploit this vulnerability by sending a D-Bus method call with conflicting publish flags. This can lead to a denial of service (DoS) by crashing the avahi-daemon, making the service unavailable.
Remediation
For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-18910

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 4 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

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.

What

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.

Why

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

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.

Why

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
local access → Reachable Assertion → disrupt the affected service
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-617 ↗

CWE-617: Reachable Assertion. The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
Denial of serviceCWE-617Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-0975avahi: Schwachstelle ermöglicht Denial of Service

Ein lokaler Angreifer kann eine Schwachstelle in avahi ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0435Multiples vulnérabilités dans les produits Microsoft

De multiples vulnérabilités ont été découvertes dans les produits Microsoft. Elles permettent à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-010926Avahiにおける到達可能なアサーションに関する脆弱性

Avahiは、mDNS/DNS-SDプロトコルスイートを介してローカルネットワーク上でサービス検出を容易にするシステムです。バージョン0.9-rc4以前のAvahiでは、権限のないローカルユーザーが競合する公開フラグを含む単一のD-Busメソッド呼び出しを送信することでavahi-daemonをクラッシュさせることが可能でした。この問題はバージョン0.9-rc4で修正されました。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 3 Apr 2026 · Last source change 11 Apr 2026, 18:09 UTC · CWE-617 · Reachable Assertion

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-18910
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 0.9-rc4 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    < 0.9-rc4 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
    Red Hat Product Security ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    avahi as a component of Red Hat Enterprise Linux 10; avahi-compat-howl as a component of Red Hat Enterprise Linux 10; avahi-compat-howl-devel as a component of Red Hat Enterprise Linux 10; avahi-compat-libdns_sd as a component of Red Hat Enterprise Linux 10; avahi-compat-libdns_sd-devel as a component of Red Hat Enterprise Linux 10; avahi-devel as a component of Red Hat Enterprise Linux 10; avahi-glib as a component of Red Hat Enterprise Linux 10; avahi-glib-devel as a component of Red Hat Enterprise Linux 10; avahi-libs as a component of Red Hat Enterprise Linux 10; avahi-tools as a component of Red Hat Enterprise Linux 10; avahi.src as a component of Red Hat Enterprise Linux 10; avahi as a component of Red Hat Enterprise Linux 6; avahi-autoipd as a component of Red Hat Enterprise Linux 6; avahi-compat-howl as a component of Red Hat Enterprise Linux 6; avahi-compat-howl-devel as a component of Red Hat Enterprise Linux 6; avahi-compat-libdns_sd as a component of Red Hat Enterprise Linux 6; avahi-compat-libdns_sd-devel as a component of Red Hat Enterprise Linux 6; avahi-devel as a component of Red Hat Enterprise Linux 6; avahi-dnsconfd as a component of Red Hat Enterprise Linux 6; avahi-glib as a component of Red Hat Enterprise Linux 6; avahi-glib-devel as a component of Red Hat Enterprise Linux 6; avahi-gobject as a component of Red Hat Enterprise Linux 6; avahi-gobject-devel as a component of Red Hat Enterprise Linux 6; avahi-libs as a component of Red Hat Enterprise Linux 6; avahi-qt3 as a component of Red Hat Enterprise Linux 6; avahi-qt3-devel as a component of Red Hat Enterprise Linux 6; avahi-qt4 as a component of Red Hat Enterprise Linux 6; avahi-qt4-devel as a component of Red Hat Enterprise Linux 6; avahi-tools as a component of Red Hat Enterprise Linux 6; avahi-ui as a component of Red Hat Enterprise Linux 6; and 59 more · Fixed: avahi-main@aarch64 as a component of Red Hat Hardened Images; avahi-main@src as a component of Red Hat Hardened Images; avahi-main@x86_64 as a component of Red Hat Hardened Images
    After
    avahi as a component of Red Hat Enterprise Linux 10; avahi-compat-howl as a component of Red Hat Enterprise Linux 10; avahi-compat-howl-devel as a component of Red Hat Enterprise Linux 10; avahi-compat-libdns_sd as a component of Red Hat Enterprise Linux 10; avahi-compat-libdns_sd-devel as a component of Red Hat Enterprise Linux 10; avahi-devel as a component of Red Hat Enterprise Linux 10; avahi-glib as a component of Red Hat Enterprise Linux 10; avahi-glib-devel as a component of Red Hat Enterprise Linux 10; avahi-libs as a component of Red Hat Enterprise Linux 10; avahi-tools as a component of Red Hat Enterprise Linux 10; avahi.src as a component of Red Hat Enterprise Linux 10; avahi as a component of Red Hat Enterprise Linux 6; avahi-autoipd as a component of Red Hat Enterprise Linux 6; avahi-compat-howl as a component of Red Hat Enterprise Linux 6; avahi-compat-howl-devel as a component of Red Hat Enterprise Linux 6; avahi-compat-libdns_sd as a component of Red Hat Enterprise Linux 6; avahi-compat-libdns_sd-devel as a component of Red Hat Enterprise Linux 6; avahi-devel as a component of Red Hat Enterprise Linux 6; avahi-dnsconfd as a component of Red Hat Enterprise Linux 6; avahi-glib as a component of Red Hat Enterprise Linux 6; avahi-glib-devel as a component of Red Hat Enterprise Linux 6; avahi-gobject as a component of Red Hat Enterprise Linux 6; avahi-gobject-devel as a component of Red Hat Enterprise Linux 6; avahi-libs as a component of Red Hat Enterprise Linux 6; avahi-qt3 as a component of Red Hat Enterprise Linux 6; avahi-qt3-devel as a component of Red Hat Enterprise Linux 6; avahi-qt4 as a component of Red Hat Enterprise Linux 6; avahi-qt4-devel as a component of Red Hat Enterprise Linux 6; avahi-tools as a component of Red Hat Enterprise Linux 6; avahi-ui as a component of Red Hat Enterprise Linux 6; and 60 more · Fixed: avahi-main@aarch64 as a component of Red Hat Hardened Images; avahi-main@src as a component of Red Hat Hardened Images; avahi-main@x86_64 as a component of Red Hat Hardened Images
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-18910↗Red Hat Product Security security advisory↗CISA Vulnrichment SSVC evidence↗Public exploit reference · GitHub GHSA-W65R-6GXH-VHVC↗Patch or update reference↗Patch or update reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-34933 · cve.blacktree.nl