I believe this is where that fact comes from [1]

Basically, 70% of high severity bugs are memory safety.

[1] https://www.chromium.org/Home/chromium-security/memory-safet...

Using the data provided, memory safety issues (use-after-free, memory-leak, buffer-overflow, null-deref) account for 67% of their bugs. If we include refcount It is just over 80%.

70% of security vulnerabilities are due to memory safety. Not all bugs.

That's the figure that Microsoft and Google found in their code bases.

probably quite a bit less than 5%, however, they tend to be quite serious when they happen

[dead]