PrintNightmare (CVE-2021-1675)

This Zeek script detects successful RpcAddPrinterDriver{,Ex} DCE RPC events, which are required to successfully exploit the vulnerability. Tests are based on exploit PCAP from Lares Lab. Tested with Zeek versions 3.0.2 and 4.0.1.

Notices

• Printer_Driver_Changed_Successfully indicates the printer driver was changed successfully.

Suricata

We have also provided Suricata rules to detect the DCE RPC commands used in this exploit. These can be either loaded into a Corelight appliance, or run directly with Suricata. These rules fire a lot on larger networks and may be sufficiently noisy so as not to be useful. Please use with caution. We have kept them here in case they are useful in other networks. In our opinion, the Zeek package is more robust against noise.

The output of running Suricata with the provided ruleset is shown below:

$ suricata -r testing/Traces/PrintNightmare.pcap -S suricata.rules
8/7/2021 -- 10:54:57 - <Notice> - This is Suricata version 6.0.3 RELEASE running in USER mode
8/7/2021 -- 10:54:57 - <Warning> - [ERRCODE: SC_WARN_ERSPAN_CONFIG(329)] - ERSPAN Type I is no longer configurable and it is always enabled; ignoring configuration setting.
8/7/2021 -- 10:54:57 - <Notice> - all 17 packet processing threads, 4 management threads initialized, engine started.
8/7/2021 -- 10:54:57 - <Notice> - Signal Received.  Stopping engine.
8/7/2021 -- 10:54:57 - <Notice> - Pcap-file module read 1 files, 53 packets, 19124 bytes

$ cat fast.log
07/02/2021-08:11:57.785982  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.824060  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.848240  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.848240  [**] [1:3000008:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriverEx [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.894097  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.894097  [**] [1:3000008:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriverEx [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.959051  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:57.959051  [**] [1:3000008:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriverEx [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:58.000581  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:58.000581  [**] [1:3000008:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriverEx [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:11:58.007953  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:12:08.520328  [**] [1:3000007:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriver [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445
07/02/2021-08:12:08.520328  [**] [1:3000008:2] CORELIGHT Possible CVE-2021-34527 (PrintNightmare) Exploit - SpoolSS RpcAddPrinterDriverEx [**] [Classification: Potentially Bad Traffic] [Priority: 2] {TCP} 192.168.1.149:50070 -> 192.168.1.157:445

References

• https://github.com/LaresLLC/CVE-2021-1675
• https://github.com/afwu/PrintNightmare
• https://github.com/cube0x0/CVE-2021-1675