CVE-2026-47183
Description
A flaw was found in zeroconf, a Python implementation of multicast DNS (mDNS) service discovery. An unauthenticated attacker on the local network can send specially crafted mDNS messages, causing the system to store an unbounded number of error messages. This can lead to excessive memory consumption, resulting in a denial of service (DoS) where mDNS-dependent features degrade or the process terminates unexpectedly.
Statement
Zeroconf is a pure Python implementation of multicast DNS (mDNS) service discovery. Prior to 0.149.6, the exception-deduplication cache that tracks malformed-packet decode errors grows without bound, retaining full tracebacks (including raw packet buffers) keyed by attacker-influenced error messages, leading to unbounded memory growth, resulting in denial of service impact for unauthenticated hosts on the local network segment (UDP/5353, 224.0.0.251 / ff02::fb). Exploitation requires the attacker to be on the same local link as the affected host, consistent with Red Hat's Adjacent (AV:A) attack vector scoring. This issue is fixed upstream in zeroconf 0.149.6.
Red Hat's CVSS score matches the vendor/CVE.org assessment for this flaw. This flaw is one of a batch of related Zeroconf issues discovered and fixed close together (CVE-2026-47180, CVE-2026-47183, CVE-2026-47184, CVE-2026-48045, CVE-2026-48487); all affect the same Red Hat product streams in the same way and were triaged consistently as a batch.
Mitigation
Upgrade to zeroconf 0.149.6 or later once packaged in the affected Red Hat product. Where upgrading isn't immediately possible, restricting the affected host's exposure to the local network segment (network segmentation or firewalling multicast DNS traffic on UDP/5353) reduces the practical attack surface, since exploitation requires local-link access.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | N/A | 6.5 |
| Attack Vector | Adjacent Network | N/A | Adjacent Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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