NVD / CVE Program· CNA GitHub_M

CVE-2025-59529: Avahi: simple protocol server ignores accepts unlimited connections and logs failures without limit

Noroxi assessment

Priority: Monitor (action score 22/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.22% (FIRST EPSS).
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: azl3 avahi 0.8-8 on Azure Linux 3.0 Release Notes; azl3 avahi 0.8-9 on Azure Linux 3.0 Release Notes; cbl2 avahi 0.8-5 on CBL-Mariner 2.0 Release Notes.

Low priority for now. Upgrade to azl3 avahi 0.8-8 on Azure Linux 3.0 Release Notes; azl3 avahi 0.8-9 on Azure Linux 3.0 Release Notes; cbl2 avahi 0.8-5 on CBL-Mariner 2.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions up to and including 0.9-rc5, the simple protocol server ignores the documented client limit and accepts unlimited connections, allowing for easy local DoS. Although `CLIENTS_MAX` is defined, `server_work()` unconditionally `accept()`s and `client_new()` always appends the new client and increments `n_clients`. There is no check against the limit. When client cannot be accepted as a result of maximal socket number of avahi-daemon, it logs unconditionally error per each connection. Unprivileged local users can exhaust daemon memory and file descriptors, causing a denial of service system-wide for mDNS/DNS-SD. Exhausting local file descriptors causes increased system load caused by logging errors of each of request. Overloading prevents glibc calls using nss-mdns plugins to resolve `*.local.` names and link-local addresses. As of time of publication, no known patched versions are available, but a candidate fix is available in pull request 808, and some workarounds are available. Simple clients are offered for nss-mdns package functionality. It is not possible to disable the unix socket `/run/avahi-daemon/socket`, but resolution requests received via DBus are not affected directly. Tools avahi-resolve, avahi-resolve-address and avahi-resolve-host-name are not affected, they use DBus interface. It is possible to change permissions of unix socket after avahi-daemon is started. But avahi-daemon does not provide any configuration for it. Additional access restrictions like SELinux can also prevent unwanted tools to access the socket and keep resolution working for trusted users.

MediumCVSS 5.5 · v3.1—No exploit Fix available

Published: Dec 18, 2025
Updated: Oct 23, 2026
EPSS: 0.2% · 12th percentile
CWE: CWE-400

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 22 / 40 · 5.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: proof of concept
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 5.5; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
avahi	avahi	cpe:2.3:a:avahi:avahi

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

avahi avahibefore 0.9
avahi avahi0.9

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

avahi avahi
- <= 0.9-rc5affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	avahi	from 0	—
openSUSE:Leap 16.0	avahi	before 0.8-160000.6.1	0.8-160000.6.1
openSUSE:Leap 16.0	avahi-glib2	before 0.8-160000.6.1	0.8-160000.6.1
openSUSE:Leap 16.0	avahi-qt6	before 0.8-160000.6.1	0.8-160000.6.1
openSUSE:Tumbleweed	avahi	before 0.8-45.1	0.8-45.1
Red Hat:hummingbird:1	avahi	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-autoipd	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-compat-howl	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-compat-howl-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-compat-libdns_sd	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-compat-libdns_sd-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-dnsconfd	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-glib	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-glib-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-gobject	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-gobject-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-libs	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt3	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt3-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt4	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt4-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt5	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1
Red Hat:hummingbird:1	avahi-qt5-devel	before 0:0.9~rc2-8.1.hum1	0:0.9~rc2-8.1.hum1

+16

Same product

avahi: all records

Other highest-scoring records for the same primary product.

CVE-2008-5081The originates_from_local_legacy_unicast_socket function (avahi-core/server.c) in avahi-daemon in Avahi before 0.6.24 allows remote attacker
40Plan
CVE-2017-6519avahi-daemon in Avahi through 0.6.32 and 0.7 inadvertently responds to IPv6 unicast queries with source addresses that are not on-link, whic
37Monitor
CVE-2021-26720avahi-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
31Monitor

Published before and after this one in the same product

← EarlierCVE-2023-38472Nov 2, 2023 · Reachable assertion in avahi_rdata_parse
22Monitor
← EarlierCVE-2023-38473Nov 2, 2023 · Reachable assertion in avahi_alternative_host_name
22Monitor
Later →CVE-2025-68276Jan 12, 2026 · Avahi has a reachable assertion in avahi_wide_area_scan_cache
22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
azl3 avahi 0.8-8 on Azure Linux 3.0	Release Notes	Microsoft (MSRC)
azl3 avahi 0.8-9 on Azure Linux 3.0	Release Notes	Microsoft (MSRC)
cbl2 avahi 0.8-5 on CBL-Mariner 2.0	Release Notes	Microsoft (MSRC)
opensuse:avahi	0.8-45.1 · openSUSE:Tumbleweed	Package registry (OSV)
opensuse:avahi-glib2	0.8-160000.6.1 · openSUSE:Leap 16.0	Package registry (OSV)
opensuse:avahi-qt6	0.8-160000.6.1 · openSUSE:Leap 16.0	Package registry (OSV)
red hat:avahi	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-autoipd	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-compat-howl	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-compat-howl-devel	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-compat-libdns_sd	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-compat-libdns_sd-devel	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-devel	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-dnsconfd	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-glib	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-glib-devel	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-gobject	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
red hat:avahi-gobject-devel	0:0.9~rc2-8.1.hum1 · Red Hat:hummingbird:1	Package registry (OSV)
suse:avahi	0.8-160000.6.1 · SUSE:Linux Enterprise Server 16.0	Package registry (OSV)
suse:avahi-glib2	0.8-160000.6.1 · SUSE:Linux Enterprise Server 16.0	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone with local access to the system can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

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

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}