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Nmap 7.8 Assertion failed: htn.toclock_running == true #1764

lpesyna opened this issue Sep 27, 2019 · 2 comments


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commented Sep 27, 2019

I am now getting this error when I attempt to do a full discovery sweep on our Class C systems. Using a local Windows 7 PC, no router hop, using syn scans as some devices do not respond to ping.

This is new to us in version 7.8, We have used these routines in version 7.7, 7.6, 6.x, and prior.

Assertion failed: htn.toclock_running == true, file ..\, line 503

The command for a specific instance is as below.

"C:\Program Files (x86)\Nmap\nmap.exe" -v -T2 -p21,23,80 -n -oA c:\uploads\local -Pn --exclude,

By trial an error I have found the threshold for triggering the error is a target range on or around 104 IP addresses. Setting --max-parallelism to 10 (random choice) prevents the error in the situations I tried.

Of course, I am unable to reproduce this in our lab environment, it only has occurred in our production subnets,


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commented Oct 4, 2019

Same on my Windows 10 with freshly instaled nmap 7.8
Setting --max-parallelism to 10 or even 100 - helps.


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commented Oct 4, 2019

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