This happened to OpenBSD in February of 2007...note the dates:
# 2007-02-21: Core sends draft advisory and proof of concept code that demonstrates remote kernel panic.
# 2007-02-26: OpenBSD team develops a fix and commits it to the HEAD branch of source tree.
And later on Core managed to upgrade the bug to "arbitrary code" vulnerability:
# 2007-03-05: Core develops proof of concept code that demonstrates remote code execution in the kernel context by exploiting the mbuf overflow.
# 2007-03-07: OpenBSD team commits fix to OpenBSD 4.0 and 3.9 source tree branches and releases a "reliability fix" notice on the project's website.
http://www.coresecurity.com/content/open-bsd-advisorie