Two vulnerabilities have been discovered and fixed in CVS:
Sebastian Krahmer discovered a vulnerability whereby a malicious CVS pserver could create arbitrary files on the client system during an update or checkout operation, by supplying absolute pathnames in RCS diffs.
Derek Robert Price discovered a vulnerability whereby a CVS pserver could be abused by a malicious client to view the contents of certain files outside of the CVS root directory using relative pathnames containing "../".
For the current stable distribution (woody) these problems have been fixed in version 1.11.1p1debian-9woody2.
For the unstable distribution (sid), these problems will be fixed soon.
We recommend that you update your cvs package.