I love C, but it's pretty scary sometime. 5 minutes ago, "I wonder if I can find a potential memory overwrite in 5 minutes?"

Sure enough, the function StrAppend potentially overflows a size_t size (without checking), and then writes into memory could be past the end of the allocated buffer. Given 5 minutes, I didn't look thoroughly if this is actually exploitable, but it's definitely a red-flag for the code. Be careful out there! Hopefully I am missing something, or this is just a simple oversight, but I would carefully audit this code before using it.

Submitted a ticket through the Althttpd website.

static char StrAppend(char zPrior, const char zSep, const char zSrc){ char zDest; size_t size; size_t n0, n1, n2;

  if( zSrc==0 ) return 0;
  if( zPrior==0 ) return StrDup(zSrc);
  n0 = strlen(zPrior);
  n1 = strlen(zSep);
  n2 = strlen(zSrc);
  size = n0+n1+n2+1;
  zDest = (char*)SafeMalloc( size );
  memcpy(zDest, zPrior, n0);
  free(zPrior);
  memcpy(&zDest[n0],zSep,n1);
  memcpy(&zDest[n0+n1],zSrc,n2+1);
  return zDest;
}