p5-Imager -- possibly exploitable buffer overflow

Imager 0.56 and all earlier versions with BMP support have
a security issue when reading compressed 8-bit per pixel BMP
files where either a compressed run of data or a literal run
of data overflows the scan-line.
Such an overflow causes a buffer overflow in a malloc()
allocated memory buffer, possibly corrupting the memory arena
headers.
The effect depends on your system memory allocator, with glibc
this typically results in an abort, but with other memory
allocators it may be possible to cause local code execution.