Overview
CVE-2025-58436 is a medium severity denial-of-service (DoS) vulnerability affecting OpenPrinting CUPS (Common UNIX Printing System) versions prior to 2.4.15. This vulnerability allows a malicious client sending slow messages to the CUPS daemon (cupsd) to exhaust resources and render the printing service unusable for other clients. Organizations relying on CUPS for their printing infrastructure should take immediate action to mitigate this risk.
Published: 2025-11-29T03:15:59.323
Technical Details
The vulnerability stems from the way cupsd handles client connections. A client initiating a connection and sending data at a very slow rate (e.g., one byte per second) can tie up a cupsd worker thread. Because CUPS has a limited number of worker threads, a sufficient number of slow connections can exhaust all available threads, effectively preventing legitimate clients from connecting and printing. This constitutes a denial-of-service condition.
The root cause lies in the lack of proper timeouts or resource management when handling slow clients. Without these safeguards, malicious actors can exploit this behavior to disrupt printing services.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns a score of 5.1 to CVE-2025-58436, indicating a MEDIUM severity. The CVSS vector is likely something like: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L (Network, Low Attack Complexity, No Privileges Required, No User Interaction, Unchanged Scope, No Confidentiality Impact, No Integrity Impact, Limited Availability Impact).
While the impact is limited to availability (i.e., preventing printing), the ease of exploitation (no authentication required) makes this vulnerability a significant concern for publicly accessible CUPS servers.
Possible Impact
Successful exploitation of CVE-2025-58436 can lead to:
- Denial of Service: The primary impact is the inability to print documents for all users connected to the affected CUPS server.
- Business Disruption: This can significantly disrupt business operations, especially in environments heavily reliant on printing.
- Reputational Damage: Service outages can lead to negative perceptions of reliability and security.
Mitigation and Patch Steps
The recommended mitigation is to upgrade to CUPS version 2.4.15 or later. This version includes a patch that addresses the slow client connection issue.
- Upgrade CUPS: The most effective solution is to upgrade your CUPS installation to version 2.4.15 or later. Use your distribution’s package manager (e.g., apt, yum, dnf) to perform the upgrade.
- Firewall Rules: Consider implementing firewall rules to restrict access to the CUPS port (typically 631) to trusted networks or IP addresses.
- Monitor CUPS: Implement monitoring solutions to detect unusual activity or resource exhaustion within the CUPS service.
