The security issues in the Windows Print Spooler don’t seem to end, as Microsoft has acknowledged yet another remote code execution (RCE) vulnerability in the subsystem.
Tracked as CVE-2021-36958 with a CVSS score of 7.3, the yet-unpatched bug is the latest to join a series of flaws collectively known as PrintNightmare that have plagued the printer service over the last few months.
Surprisingly though, Microsoft’s acknowledgement of the vulnerability, comes over eight months after it was reported by a cybersecurity researcher in December 2020.
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“An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights,” says Microsoft explaining the newest vulnerability.
Will Dormann, a vulnerability analyst for CERT/CC, told BleepingComputer that Microsoft has confirmed that the CVE-2021-36958 vulnerability corresponds to a proof-of-concept shared by security researcher Benjamin Delpy on Twitter last month.
Delpy’s trick, explains BleepingComputer, uses the CopyFile registry directive to copy a DLL file, which then opens a command prompt to the client when you connect to a printer.
While Microsoft has since tweaked the permissions of the Point and Print feature to require administrative privileges, Delpy PoC will still work since it requires an already-installed driver.
In any case, Microsoft says it is now working to patch the bug. However, in the absence of a fix, Microsoft suggests the only available workaround to mitigate CVE-2021-36958 is to stop and disable the Print Spooler service.