Apply by doing:
       cd /usr/src
       patch -p0 < 002_cvs.patch

And then rebuild and install cvs:
       cd gnu/usr.bin/cvs
       make -f Makefile.bsd-wrapper obj
       make -f Makefile.bsd-wrapper
       make -f Makefile.bsd-wrapper install

Index: gnu/usr.bin/cvs/src/client.c
===================================================================
RCS file: /cvs/src/gnu/usr.bin/cvs/src/client.c,v
retrieving revision 1.10
retrieving revision 1.10.8.1
diff -u -p -r1.10 -r1.10.8.1
--- gnu/usr.bin/cvs/src/client.c        6 Jul 2002 04:41:29 -0000       1.10
+++ gnu/usr.bin/cvs/src/client.c        1 May 2004 00:19:41 -0000       1.10.8.1
@@ -1003,6 +1003,20 @@ call_in_directory (pathname, func, data)
    char *rdirp;
    int reposdirname_absolute;

+    /*
+     * For security reasons, if PATHNAME is absolute or attempts to
+     * ascend outside of the current sandbox, we abort.  The server should not
+     * send us anything but relative paths which remain inside the sandbox
+     * here.  Anything less means a trojan CVS server could create and edit
+     * arbitrary files on the client.
+     */
+    if (isabsolute (pathname) || pathname_levels (pathname) > 0)
+    {
+        error (0, 0,
+               "Server attempted to update a file via an invalid pathname:");
+        error (1, 0, "`%s'.", pathname);
+    }
+
    reposname = NULL;
    read_line (&reposname);
    assert (reposname != NULL);
Index: gnu/usr.bin/cvs/src/modules.c
===================================================================
RCS file: /cvs/src/gnu/usr.bin/cvs/src/modules.c,v
retrieving revision 1.2
retrieving revision 1.2.2.1
diff -u -p -r1.2 -r1.2.2.1
--- gnu/usr.bin/cvs/src/modules.c       12 Dec 2003 14:43:56 -0000      1.2
+++ gnu/usr.bin/cvs/src/modules.c       1 May 2004 00:19:41 -0000       1.2.2.1
@@ -170,6 +170,13 @@ do_module (db, mname, m_type, msg, callb
    if (isabsolute (mname))
       error (1, 0, "Absolute module reference invalid: `%s'", mname);

+    /* Similarly for directories that attempt to step above the root of the
+     * repository.
+     */
+    if (pathname_levels (mname) > 0)
+       error (1, 0, "up-level in module reference (`..') invalid: `%s'.",
+               mname);
+
    /* if this is a directory to ignore, add it to that list */
    if (mname[0] == '!' && mname[1] != '\0')
    {