It was discovered that an integer overflow in the SFTP file transfer module of the ProFTPD daemon could lead to denial of service.
The oldstable distribution (lenny) is not affected.
For the stable distribution (squeeze), this problem has been fixed in version 1.3.3a-6squeeze1.
For the unstable distribution (sid), this problem has been fixed in version 1.3.3d-4.
We recommend that you upgrade your proftpd-dfsg packages.