CVE-2025-8283

Executive Summary

CVE-2025-8283 is a medium-severity vulnerability in the netavark network stack used by Podman for container networking. The flaw arises because the dns.podman search domain is not appended to the container's DNS resolver configuration. When a container is created with a given name, that name becomes the container's hostname. Without the internal search domain, the container falls back to the host's resolv.conf search domains. If any of those external domains contain a hostname matching the container's name, DNS queries can be resolved to unintended external servers, leading to potential traffic redirection or information disclosure.

This vulnerability is particularly dangerous in multi-tenant environments or when containers are named after common hostnames (e.g., db, api, web). An attacker controlling an external domain that matches the container name could intercept traffic intended for internal services.

Supply Chain & Package Security

This vulnerability affects the netavark package, which is a core component of the Podman container ecosystem. Netavark is written in Rust and is distributed as a system package (RPM, DEB) or built from source. The supply chain risk is moderate: if an organization uses a vulnerable version of netavark, all containers using the default DNS configuration are affected. The fix is available in netavark v1.12.0 and podman v4.18.0. Users should update these packages from trusted repositories.

CVSS Breakdown & Threat Level

• CVSS Score: 3.7 (Low)
• Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector: Network (AV:N) – The vulnerability can be triggered remotely.
• Attack Complexity: High (AC:H) – Requires an attacker to control a domain that matches the container hostname and have that domain in the host's search list.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: Low (C:L) – Limited information disclosure (DNS resolution leakage).
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Low. Exploitation requires specific conditions (attacker-controlled domain matching container hostname, host search domain containing that domain). However, in cloud or multi-tenant environments, the risk increases.

Deep Dive & Mechanics

The vulnerability lies in how netavark configures DNS for containers. When a container is created with podman run --name mycontainer, the container's hostname is set to mycontainer. Netavark is responsible for setting up the container's network namespace, including /etc/resolv.conf. In vulnerable versions, netavark fails to add the dns.podman search domain (or equivalent internal domain) to the container's resolver configuration.

Without this internal search domain, the container inherits the host's /etc/resolv.conf search domains. For example, if the host has search example.com internal.corp, and the container is named db, a DNS query for db will be expanded to db.example.com and db.internal.corp. If an attacker controls db.example.com (e.g., by registering the domain or poisoning DNS), the container's traffic intended for an internal db service could be redirected to the attacker's server.

The core issue is a missing search domain entry. The fix ensures that netavark appends a container-specific search domain (e.g., dns.podman) so that unqualified hostnames are resolved within the container's own network first.

Vulnerable vs. Patched Code

Vulnerable Code (netavark < 1.12.0): In the DNS configuration logic, the search domain list is not populated with the container's internal domain. The container's /etc/resolv.conf might look like:

nameserver 8.8.8.8
search example.com

No dns.podman entry.

Patched Code (netavark >= 1.12.0): The fix adds the internal search domain. The container's /etc/resolv.conf now includes:

nameserver 8.8.8.8
search dns.podman example.com

This ensures that db resolves to db.dns.podman first, which is handled by the internal DNS resolver (e.g., dnsmasq or CoreDNS) and not leaked to external servers.

The patch is implemented in the netavark Rust source, specifically in the DNS configuration module. The commit adds logic to prepend the container's search domain to the list.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Control a domain (e.g., evil.com) that is in the host's search list.
• The container must be named with a hostname that matches a subdomain of your domain (e.g., container named api, host search domain includes evil.com).

Lab Setup:

1. Set up a DNS server for evil.com with an A record for api.evil.com pointing to your attacker machine.
2. On the victim host, ensure /etc/resolv.conf contains search evil.com.
3. Create a container: podman run --name api -d nginx
4. Inside the container, run curl http://api – this will resolve to api.evil.com (your attacker server) instead of an internal service.

Exploitation Steps:

1. Register a domain that matches common container names (e.g., db.evil.com, web.evil.com).
2. Poison the host's DNS search list (if possible) or rely on existing search domains.
3. Wait for containers to be created with matching names.
4. Capture traffic or serve malicious content.

Blue Team (Defender)

Detection:

• Monitor DNS queries from containers for unexpected external resolutions.
• Check container /etc/resolv.conf for missing internal search domains.
• Use network monitoring to detect traffic to unexpected external IPs from containers.

Mitigation:

• Update netavark to v1.12.0+ and podman to v4.18.0+.
• Manually add the internal search domain to container configurations: podman run --dns-search dns.podman ...
• Restrict container hostnames to avoid conflicts with external domains.
• Use a dedicated internal DNS resolver that overrides external queries.

Indicators of Compromise (IOCs)

• Network: DNS queries from containers to external domains matching container hostnames (e.g., api.evil.com).
• File: Container /etc/resolv.conf missing dns.podman or similar internal search domain.
• Process: Unusual outbound connections from containers to IPs not in the internal network.
• Log: Podman or netavark logs showing DNS configuration without internal search domain.

Detection Engineering

YARA Rule

rule Detect_Missing_Internal_Search_Domain_in_Container_Resolv {
    meta:
        description = "Detects container /etc/resolv.conf files missing the internal search domain (dns.podman)"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-8283"
    strings:
        $search_line = /^search\s+/
        $internal_domain = "dns.podman"
    condition:
        $search_line and not $internal_domain
}

Sigma Rule

title: Container DNS Resolution Leak via Missing Internal Search Domain
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects containers whose /etc/resolv.conf lacks the internal search domain, indicating potential DNS leakage (CVE-2025-8283).
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/podman'
        CommandLine|contains: 'run'
    filter:
        CommandLine|contains: '--dns-search'
    condition: selection and not filter
falsepositives:
    - Containers intentionally using external DNS only
level: medium

Suricata Rule

alert dns any any -> any any (msg:"CVE-2025-8283 - Container DNS Query to External Domain Matching Hostname"; dns_query; content:"|01 00 00 01 00 00 00 00 00 00|"; distance:0; within:12; content:"|07|example|03|com|00|"; nocase; sid:1000001; rev:1;)

Note: Replace example.com with the actual external domain in the search list. This rule is a template and should be customized.

Remediation & Mitigation

Immediate:

• Update netavark to v1.12.0 or later.
• Update podman to v4.18.0 or later.
• Restart all containers to apply the new DNS configuration.

Short-term:

• Manually add --dns-search dns.podman to all podman run commands.
• Audit container hostnames to avoid conflicts with external domains.
• Implement network segmentation to limit container egress.

Long-term:

• Use a dedicated internal DNS resolver (e.g., CoreDNS) that handles container hostnames.
• Monitor DNS queries from containers for anomalies.
• Apply principle of least privilege to container networking.

Patch Details:

• Netavark: Update to version >= 1.12.0. Available from GitHub releases or package manager.
• Podman: Update to version >= 4.18.0. Available from official repositories.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert
Report generated for CVE-2025-8283