Finding HP printers and MFPs vulnerable to Printing Shellz

(updated ), by Pearce Barry
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Do you have HP printers and multi-function printers (MFPs)? You might want to look at the two recently published vulnerabilities that affect 150+ models. Named “Printing Shellz” by the F-Secure security researchers who reported them, these vulns have been around for ~8 years.

When successfully exploited, can provide attackers with:

  • CVE-2021-39237, “medium” CVSS score of 4.6 - Information disclosure via exposed connectors to gain shell access (requires physical access to the vulnerable device).
  • CVE-2021-39238, “critical” CVSS score of 9.8 - Remote code execution via buffer overflow in the font parsing logic.

HP LaserJet, PageWide, OfficeJet, and ScanJet product lines all contain vulnerable models. You can find the full lists in HP’s posted advisories: CVE-2021-39237 and CVE-2021-39238.

HP released patched firmware last month and urged owners of affected printers to update their firmware as soon as possible. F-Secure’s researchers also offer some mitigation strategies, as well in section 6 of their writeup.

How to find vulnerable HP printers and MFPs with runZero

From the Asset Inventory, use the following pre-built query to locate potentially vulnerable HP printer and MFP assets within your network:

NOT hardware:"JetDirect" AND (mac_vendor:"HP" OR mac_vendor:="Hewlett Packard%" OR hardware:"HP%" OR hardware:="Hewlett Packard%") AND (type:printer OR os.family:"LaserJet" OR NOT (os:"%iLO%" OR type:switch OR type:computer))
Find HP printers

You can also search via the Service Inventory, using the following pre-built query to locate potentially HP printer and MFP services within your network:

_asset.protocol:http AND protocol:http AND ((html.title:="HP %LaserJet%" OR banner:="HP %LaserJet%") OR (html.title:="HP %PageWide%" OR banner:="HP %PageWide%") OR (html.title:="HP %OfficeJet%" OR banner:="HP %OfficeJet%") OR (html.title:="HP %ScanJet%" OR banner:="HP %ScanJet%"))
Find HP printers

Note that results from the above queries may contain models that are not vulnerable, so manual verification against the full lists of affected models published by HP (here and here) is needed.

As always, any prebuilt queries we create are available from our Queries Library. Check out the library for other useful inventory queries.

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