[File a bug report for the Demon Implant]: exception occurred in BeaconPrintf because vsnprintf

[sh1xo]

Contact Details

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What happened?

When the first parameter buffer is NULL, vsnprintf return -1, which causes an exception in BeaconPrintf. This happens when I execute the locale bof. (https://github.com/HavocFramework/Havoc/blob/c393115fa1714748f368aff97e55da4aa81f5c56/payloads/Demon/Source/Loader/ObjectApi.c#L217C5-L217C5)

and this works for me

    va_start(VaListArg, fmt);

    //CallbackSize = Instance.Win32.vsnprintf(NULL, 0, fmt, VaListArg);
    CallbackSize = 0x1000; //big enough
    CallbackOutput  = Instance.Win32.LocalAlloc( LPTR, CallbackSize );

    Instance.Win32.vsnprintf(CallbackOutput, CallbackSize, fmt, VaListArg);

    va_end(VaListArg);

Did You Do a Pull First?

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Did You Try With the Dev Branch?

No (You only tried the main branch...)

Relevant log output

No response

Did You Read Over Your Issue First?

• [X] I declare I made an effort and provided the necessary information for replication of the issue.

[S4ntiagoP]

hey there, I added some sanity checks to BeaconPrintf, which should make it more robust, reopen this if needed!