Microsoft is sharing an urgent new warning with users of its Windows software, this one about an unpatched vulerability that hackers are apparently actively exploiting. This bug, which has been referred to as Windows PrintNightmare, seems to affect pretty much all Windows users.
That’s according to the warning Microsoft issued in recent days, noting that “the code that contains the vulnerability is in all versions of Windows.” However, as noted by The Verge, it’s unclear if this bug is exploitable outside of server versions of Windows.
Windows ‘PrintNightmare’ vulnerability
So, what’s going on here? As Microsoft explains in its warning, the company is aware of and investigating a remote code execution vulnerability that affects the Windows Print Spooler service. “This is an evolving situation,” the company warns — and the vulnerability also sounds as bad as it gets. Per Microsoft, “An attacker who successfully exploited this vulnerability could run arbitrary code with system privileges.”
It also seems that a series of misunderstandings led to knowledge about this particular security vulnerability becoming public. Researchers at Sangfor in recent days published a proof-of-concept exploit about all this (accidentally, according to The Verge). The code, however, ended up being making its way to GitHub before Sangfor took it down.
We deleted the POC of PrintNightmare. To mitigate this vulnerability, please update Windows to the latest version, or disable the Spooler service. For more RCE and LPE in Spooler, stay tuned and wait our Blackhat talk. https://t.co/heHeiTCsbQ
— zhiniang peng (@edwardzpeng) June 29, 2021
Sangfor researchers had been planning to walk through the PrintNightmare vulnerability in Windows Print Spooler later this month, at the Black Hat security conference in Vegas. Microsoft had already published fixes for a different Print Spooler problem. So Sangfor might have thought this one was patched and okay to talk about publicly.
In terms of how serious this vulnerability is, a BleepingComputer report notes that the remote code execution that allows hackers to take over servers with system privileges would enable them to “install programs, view, change, or delete data, and create new accounts with full user rights.”
As of the time of this writing, BleepingComputer goes on to warn that no security updates are available to address the PrintNightmare zero-day vulnerability. Microsoft is apparently still in the investigating phase of this problem as it works toward a fix for it.
Two other critical points: Again, Microsoft confirmed that hackers have definitely exploited this vulnerability already. One step Windows users can take is making sure they’ve installed security updates released around the beginning of June.
Other reports have noted that Windows users can disable the Printer Spooler service. Additionally, users can disable inbound remote printing through Group Policy.