This paper presents an experimental study which shows that, for the Intel x86 architecture, single-bit control flow errors in the authentication sections of targeted applications can result in significant security vulnerabilities. The experiment targets two well-known Internet server applications: FTP and SSH (secure shell), injecting single-bit control flow errors into user authentication sections of the applications. The injected sections constitute approximately 2-8% of the text segment of the target applications. The results show that out of all activated errors (a) 1-2% compromised system security (create a permanent window of vulnerability), (b) 43-62% resulted in crash failures (about 8.5% of these errors create a transient window of vulnerability), and (c) 7-12% resulted in fail silence violations. A key reason for the measured security vulnerabilities is that, in the x86 architecture, conditional branch instructions are a minimum of one Hamming distance apart. The design and evaluation of a new encoding scheme that reduces or eliminates this problem is presented.