A Mac programmer backed up his criticism of an allegedly exploitable flaw in the Mac OS X's disk image (.dmg) format with an analysis published on Thursday that appears to show that the flaw, at most, causes a crash of the system.

While the common wisdom in the security world is that crashes are exploitable, Mac programmer Alastair Houghton published his kernel-code analysis showing that this particular vulnerability is not.

"In fact, all (the MoKB) has found here is a bug that causes a kernel panic," Houghton wrote in his analysis. "Not a security flaw. Not a memory corruption bug. Just a completely orderly kernel panic."

Following the analysis, Secunia downgraded their severity rating of the vulnerability from "highly critical" to "not critical." Several other companies still have the vulnerability rated as critical.

The actions follow a heated exchange between Houghton and the founder of the Month of Kernel Bugs (MoKB) Project, a person who identifies himself as only L.M.H. Because of the exchange, Houghton decided to spend three days analyzing the issue and had his final analysis checked by Thomas Ptacek, a security researcher and founder of Matasano Security.

In online comments, MoKB founder L.M.H acknowledged that Houghton's analysis might be correct.

"Your point here is that this particular issue isn't exploitable. The advisory states a potential risk. Enough said," he wrote in comments on the MoKB blog.

In comments to SecurityFocus and online, L.M.H. stated that he has found other issues with Apple's disk image format and may release them in the future.