[FIX]: Prevent crash in dialParallel by adding nil checks and variable fix #475
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This resolves issue #5934 reported in the nuclei repository. This commit fixes a critical crash in the dialParallel method of DialWrap where the receiver could be nil, causing a runtime panic. Added explicit nil checks for both the DialWrap receiver and its internal dialer before proceeding with dialing operations. Also corrected a variable misuse inside startRacer from 'ras' to 'targets' to avoid undefined identifier errors. These changes improve the stability and reliability of connection dialing in fastdialer, preventing unexpected crashes when dialing with primary and fallback IP lists.
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The undefined: fmt error was caused by the missing import of the "fmt" package.
tarunKoyalwar
requested changes
Jul 26, 2025
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thanks for the pr @Mehran-Seifalinia , but the issue linked seems to be different , we are adding a nil check for case when the method receiver is nil which shouldn't be the case, most likely the global fastdialer used in httpclientpool is being closed or is nil , that seems to be the root cause
this will hide the panic but won't fix the issue and it will cause on a different method call of dialer
cc: @dwisiswant0 , seems like we have a case where global fastdialer instance is being closed early
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@Mehran-Seifalinia I'm closing the PR as introducing the changes would break current functionalities. We will keep an eye on the issue and will try to nail down a fix within nuclei. Thanks for your contribution! |
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Summary
This pull request addresses a critical crash issue in the
dialParallelmethod of theDialWrapstruct, caused by a missing nil receiver check and an incorrect variable reference inside the internalstartRacerfunction.Changes
DialWrapreceiver (d) to prevent runtime panics when it is nil.dialerfield to ensure safe dialing operations.startRacerfunction: replaced undefinedraswithtargets.Impact
These changes improve the stability and robustness of the dialing mechanism used by
fastdialer, preventing crashes reported in issue #5934 when running nuclei against large lists of websites.Testing
The fix was tested locally by simulating nil receiver conditions and dialing with various IP sets, confirming no crashes and proper fallback behavior.
Closes #5934