Understanding the New Vulnerabilities on Linux’s CUPS: What You Should Know

Yesterday, a new set of vulnerabilities (CVE-2024-47076, CVE-2024-47175/6/7) was discovered on Linux’s Common UNIX Printing System (CUPS). These flaws affect multiple CUPS components, including libcupsfilters, libppd, cups-browsed, and cups-filters, and they pose the risk of remote code execution (RCE) on vulnerable Linux machines.

How the Vulnerability is Exploited

The primary vulnerability involves the cups-browsed service, which allows for the automatic discovery of network printers, similar to the functionality found in Windows and Mac environments. If enabled, this service listens on UDP port 631, accepting remote connections from printers.

An attacker with access to the internal network could create a malicious printer using a PostScript Printer Description (PPD) format. They could then advertise this fake printer to the exposed cups-browsed service, which would automatically register it as a valid network printer. If a user then attempts to print to this malicious printer, the attacker could execute arbitrary commands on the local machine, potentially leading to a full compromise.

Damage Potential

Although this vulnerability is concerning, its real-world impact is limited due to several factors:

1. Cups-browsed is not typically enabled by default, reducing the chance of widespread exposure.
2. The attack requires UDP access to the target, meaning the attacker must already be within the network, as ingress controllers, firewalls, or web application firewalls (WAFs) typically block UDP traffic to such ports.
3. The attacker must somehow convince the user to print to the malicious printer, a step that adds further difficulty in exploiting this vulnerability.

As a result, the likelihood of this vulnerability affecting production workloads is quite low, as most environments don’t have this service running.

Mitigation

There are currently no official patches for these vulnerabilities, but mitigation is simple. Disabling the vulnerable service will effectively block any potential exploitation.

sudo systemctl stop cups-browsed
sudo systemctl disable cups-browsed

Detecting the Vulnerability and Potential Exploitation of CVE-2024-10367

First, you need to detect the vulnerability in your environment and assess its potential impact on business-critical workloads. Then, apply security measures to ensure you can detect any exploit attempts in real-time.

1. Runtime Vulnerability Management

• Image Scanning: Scan container images and software to locate vulnerable CUPS versions, helping identify affected workloads for prioritizing remediation.
• Assessing Workload Criticality: Evaluate the criticality of affected workloads to ensure vital operations are secured quickly.

• Inbound Reachability: Monitor traffic to port 631 to assess exposure, especially if ingress controllers already block access.
• Runtime Status: Check if the vulnerable service is running, to estimate exploitability based on real-time activity.

2. Multi-Layered Detection Approach

Real-time detection is crucial for identifying and mitigating exploit attempts. By integrating Cloud Detection and Response (CDR), Network Detection and Response (NDR), Application Detection and Response (ADR), and Workload Detection, you gain a comprehensive view of incidents for faster MTTR.

• CDR: Monitors cloud environments for suspicious activities, such as unusual logins or unauthorized role changes. For CVE-2024-10367, CDR can detect role escalations or suspicious IP activity targeting cloud-hosted CUPS services.
• NDR: Analyzes network traffic for unauthorized access or lateral movement. In this case, NDR could flag abnormal traffic attempting to access port 631, a critical entry point for the vulnerability.
• ADR: Focuses on detecting application-level anomalies. For example, with CVE-2024-10367, ADR would detect unusual API calls such as CUPS-Create-Job or unauthorized configuration changes that may signal exploitation attempts within the CUPS service.
• Workload Detection: Monitors processes at the system level, identifying abnormal behaviors like privilege escalation or suspicious execution. For this vulnerability, it would flag suspicious activity related to /usr/sbin/cupsd, such as privilege escalations or unexpected child processes.

At Sweet Security, we empower organizations to stay ahead of emerging vulnerabilities like the one affecting Linux’s CUPS by offering a comprehensive, real-time approach to detection and mitigation. Our platform combines runtime vulnerability management with a multi-layered detection strategy, ensuring that you can quickly identify and prioritize affected workloads while monitoring for exploit attempts across your entire cloud environment. With advanced capabilities in Cloud, Network, Application, and Workload Detection and Response, Sweet ensures that every layer of your infrastructure is protected, minimizing the risk of breaches and reducing MTTR. By leveraging Sweet’s proactive security measures, your organization is well-equipped to navigate and mitigate critical threats, ensuring business continuity and safeguarding sensitive data.

Ready to see how Sweet can protect your cloud environment? Request a demo today and discover how we can help you secure your infrastructure from emerging threats like CVE-2024-10367 and beyond.