Detecting CUPS Exploits: Critical Security Vulnerabilities in Linux and Unix Systems Allow Remote Code Execution

Another day, another challenge for cyber defenders. Recently, researchers revealed a series of critical security gaps in the OpenPrinting Common Unix Printing System (CUPS), a widely used printing service in Linux environments. These vulnerabilities, if exploited, could allow attackers to execute arbitrary code remotely, potentially giving them control over affected systems. The discovery highlights a significant threat to both personal and enterprise Linux setups, as CUPS is a core component of many printing and document-handling workflows.

CUPS RCE Exploits Detection

In 2023, over 30,000 new vulnerabilities were spotted. By 2024, this figure saw a dramatic 39% increase, underscoring the growing importance of proactive vulnerability detection as a cybersecurity measure. The latest critical issues in the limelight are a set of flaws affecting CUPS (CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, CVE-2024-47177). In case exploited, the flaws might be leveraged as RCE exploit chain exposing Linux and Unix systems to the risk of compromise. 

To identify possible exploitation attempts, security professionals might rely on SOC Prime Platform for collective cyber defense. The Platform provides a set of curated detection rules accompanied by innovative solutions for advanced threat hunting, automated threat hunting, and AI-powered detection engineering. 

Hit the Explore Detections button below and immediately drill down to a collection of Sigma rules addressing CUPS vulnerability exploitation. The rules are compatible with 30+ SIEM, EDR, and Data Lake formats and mapped to MITRE ATT&CK. Additionally, detections are enriched with extensive metadata, including attack timelines, CTI links, executable binaries, triage recommendations and more.

Explore Detections

Security researchers seeking for more detection content addressing CVE exploitation attempts might access the comprehensive collection of CTI-enriched rules by browsing Threat Detection Marketplace with a “CVE” tag.

CUPS Exploit Chain Attack Analysis

A recent disclosure has revealed a new set of critical flaws in CUPS, giving attackers the green light to perform RCE under specific circumstances. Among the impacted systems are most GNU/Linux distributions, BSDs, ChromeOS, and Solaris, with many of them having the cups-browsed service enabled by default.

The RCE attack is facilitated by exploiting multiple vulnerabilities (CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177) across different CUPS components, including cups-browsed, libppd, libcupsfilters, and cups-filters. More specifically, an unauthenticated remote attacker could potentially craft an exploit chain to create a fake, malicious printer on a Linux system running CUPS that is exposed to the network, leading to RCE when a print job is sent. Given the extensive use of CUPS and the potential for remote exploitation, this poses a serious risk to organizations that rely on the impacted products. Currently, the Shodan Report reveals that more than 75K CUPS services are publicly accessible on the internet, with five regions with the highest number of exposed instances being South Korea, the U.S., Hong Kong, Germany, and China.

Varonis researchers indicate that CUPS versions up to and including 2.0.1 are vulnerable to the exploit chain. For an attack to succeed, the CUPS service must be running, and attackers require access to the active CUPS port via UDP. While firewalls can block external threats, internal systems remain exposed. Rapid7 researchers noted that impacted systems can be exploited from the public internet or within network segments only if UDP port 631 is open and the vulnerable service is active.

Before the official vulnerability disclosure, several PoC exploits circulated online. Two examples were posted on GitHub, but both contained syntax errors that could be easily fixed. The Datadog Security Research team uncovered that the third released PoC appeared to be more reliable, though it required the attacker and victim to be on the same local network.

Elastic Security Labs attempted two attack scenarios to illustrate the effects of the RCE vulnerability chain: one involving a payload for a reverse shell utilizing living-off-the-land techniques, and another for retrieving and executing a remote payload. Upon successful exploitation attempts, adversaries can take control of the system to execute arbitrary commands, which may lead to data theft, ransomware deployment, or other offensive activities, particularly in systems linked to printers over a WAN.

While patches for the vulnerabilities are on their way, the vendor has released the security advisory to minimize the risks of vulnerability exploitation. Evilsocket recommends mitigating the threat posed by the CUPS exploit chain by disabling or removing the cups-browsed service, updating the CUPS package, and blocking all traffic to UDP port 631 and DNS-SD.

With the newly uncovered CUPS vulnerabilities posing a real exploitation risk, organizations are looking for future-proof solutions to proactively thwart attacks weaponizing critical security flaws. SOC Prime’s complete product suite for AI-powered detection engineering, automated threat hunting, and advanced detection engineering equips security teams with a cutting-edge toolkit for building a robust cybersecurity posture.