What Is the Microsoft Print Spooler Vulnerability?

March 21, 2023 • Devin Partida


You may not think of printers as targets for hackers. Unfortunately, though, cybercriminals can, and often do, exploit vulnerabilities associated with them. One of the more recent instances came from a Microsoft Print Spooler vulnerability that people nicknamed PrintNightmare. Cybersecurity researchers discovered it in March 2021. 

What Is the Print Spooler?

Print Spooler is a Microsoft program responsible for managing all the jobs sent to a printer or print server. It allows people to create and manage print queues.

What Are the Risks Associated With the Print Spooler Vulnerability?

Dr. Zhiniang Peng and Xuefeng Li, two cybersecurity researchers from Sangfor Technologies, are people first associated with this print spooler vulnerability. They nicknamed it PrintNightmare and planned to discuss their findings at the Black Hat USA 2021 conference. 

After the researchers disclosed their discovery to Microsoft, classifying it as a local privilege escalation (LPE). That means it allows someone — including a hacker — to assume the access rights of a party within an organization. Usually, that internal individual is an administrator. 

The main issue is that everyday users typically have relatively low-level privileges, but they can still do everything necessary for their normal computer usage. However, once hackers find an issue that allows them to achieve a local privilege escalation, they increase their access capabilities after getting inside the system. 

However, once the researchers disclosed the issue to Microsoft, the tech company reclassified the vulnerability as a remote code execution (RCE). That means it allows a hacker to execute dangerous code on a computer. The effects could range from the machine getting infected by malware to an unauthorized person.

Printers are incredibly convenient. People can capture and print what they see on their screens. Alternatively, they might print documents related to school, an upcoming trip or something they want to buy online. However, as this issue illustrates, printers can also be gateways for cyberattacks. 

How Should You React to This Printer Threat?

In the earliest days after the disclosure of the Print Spooler vulnerability, federal cybersecurity experts in the United States encouraged administrators to disable the software. Then, a team at Forescout, another cybersecurity firm, used internal data to get an idea of how many admins followed that advice. What they found was that more people disabled it as time passed. That may be due to how the PrintNightmare vulnerability was also getting progressively more media coverage. 

Before the recommendation, only 12% of people in the study with critical assets had disabled the Print Spooler. However, after the document’s publication, that figure increased to 31%. Microsoft released a patch for the Print Spooler vulnerability on July 6, 2021. However, the Forescout research showed 65% of total assets remained vulnerable before that data. That statistic suggested the recommendation helped but didn’t do enough.

If your Windows computer does not have the latest security updates, the Print Spooler problem could still cause trouble. However, since the patch came out on July 6, the best thing to do is get that update. It’s well worth downloading more recent ones, too. Some security updates seem inconsequential. However, releases like this one are vital for protecting your printers and network against cyberattacks.

Stay Alert to Printer Threats

PrintNightmare is far from the only threat to affect printers. The risk rises as these machines have more and more connected features. That connectivity typically supports user-friendliness and productivity. However, it can help hackers access a network. No matter how and why you use printers, it’s best to follow advice from people familiar with the latest threats. Then, take action promptly to mitigate your risk.