On May 11, 2023, the Cybersecurity and Infrastructure Security Agency (CISA) and the Federal Bureau of Investigation (FBI) jointly released a Cybersecurity Advisory (CSA) in response to the active exploitation of a vulnerability, CVE-2023-27350, in PaperCut MF and NG. This article provides an overview of the advisory, including the nature of the vulnerability, the observed malicious activity, detection methods, and mitigation strategies.

The Vulnerability and Exploitation

CVE-2023-27350 is a vulnerability found in certain versions of PaperCut NG and PaperCut MF. It allows an unauthenticated actor to remotely execute malicious code without requiring any credentials. Recognizing the severity of this vulnerability, PaperCut released a patch in March 2023 to address the issue.

Malicious actors began exploiting CVE-2023-27350 in mid-April 2023 and continue to do so to this day, according to the FBI’s observations. Of particular concern is the activity of a group identifying itself as the “Bl00dy Ransomware Gang” in early May 2023. This group specifically targeted vulnerable PaperCut servers within the Education Facilities Subsector.

The Joint Advisory

The joint advisory serves to provide crucial information to network defenders, administrators, and users on detecting and mitigating the exploitation of CVE-2023-27350. It also includes indicators of compromise (IOCs) associated with the Bl00dy Ransomware Gang’s activities.

Detection methods outlined in the advisory enable organizations to identify potential exploitation attempts of the vulnerability. By implementing these methods, network defenders can proactively monitor their systems for signs of compromise. In cases where immediate patching is not possible, the advisory suggests implementing workarounds to reduce the risk of exploitation.

Mitigation and Response

CISA and the FBI emphasize the importance of applying patches promptly to address CVE-2023-27350. Organizations that have not yet patched their PaperCut installations are advised to assume compromise and initiate hunting for signs of malicious activity. The CSA provides detection signatures to aid in identifying potential compromises.

In the event that malicious activity is detected, the advisory provides incident response recommendations. Organizations should follow these recommendations to effectively mitigate the impact of an attack and minimize the potential damage caused by the Bl00dy Ransomware Gang or other threat actors exploiting the PaperCut vulnerability.

Further Resources

Read the report in PDF format:


The joint Cybersecurity Advisory from CISA and the FBI highlights the ongoing exploitation of CVE-2023-27350 in PaperCut MF and NG, underscoring the urgent need for organizations to address this vulnerability. By promptly applying patches, implementing detection methods, and following incident response recommendations, network defenders can fortify their systems against malicious actors such as the Bl00dy Ransomware Gang. Proactive measures and a robust security posture are crucial in defending against emerging threats and ensuring the integrity of critical infrastructure and data.