There are a few places where untrusted information could cause problems.
There's a bug in the configuration file parser that might result in an
LHS= modifying the rhs setting.
The case-insensitive comparison routine is probably called safely (with the
second argument at least as long as the first), but it looks weird.
--- hesiod-3.0.2/hesiod.c	Wed Oct  3 15:16:17 2001
+++ hesiod-3.0.2/hesiod.c	Wed Oct  3 15:33:41 2001
@@ -138,7 +138,8 @@
   const char *rhs;
   int len;
 	
-  strcpy(bindname, name);
+  strncpy(bindname, name, sizeof(bindname) - 1);
+  bindname[sizeof(bindname) - 1] = 0;
 
   /* Find the right right hand side to use, possibly truncating bindname. */
   p = strchr(bindname, '@');
@@ -288,7 +289,7 @@
 
       if (cistrcmp(key, "lhs") == 0 || cistrcmp(key, "rhs") == 0)
 	{
-	  which = (strcmp(key, "lhs") == 0) ? &ctx->lhs : &ctx->rhs;
+	  which = (cistrcmp(key, "lhs") == 0) ? &ctx->lhs : &ctx->rhs;
 	  *which = malloc(strlen(data) + 1);
 	  if (!*which)
 	    {
@@ -462,7 +463,7 @@
 
 static int cistrcmp(const char *s1, const char *s2)
 {
-  while (*s1 && tolower(*s1) == tolower(*s2))
+  while (*s1 && *s2 && tolower(*s1) == tolower(*s2))
     {
       s1++;
       s2++;
--- hesiod-3.0.2/hespwnam.c	Wed Oct  3 15:29:40 2001
+++ hesiod-3.0.2/hespwnam.c	Wed Oct  3 15:29:43 2001
@@ -39,9 +39,16 @@
 
 struct passwd *hesiod_getpwuid(void *context, uid_t uid)
 {
-  char uidstr[16];
+  char uidstr[32];
 
-  sprintf(uidstr, "%d", uid);
-  return getpwcommon(context, uidstr, 1);
+  if (snprintf(uidstr, sizeof(uidstr), "%ld", (long)uid) < sizeof(uidstr))
+    {
+      return getpwcommon(context, uidstr, 1);
+    }
+  else
+    {
+      errno = ERANGE;
+      return NULL;
+    }
 }
 
--- hesiod-3.0.2/hesservbyname.c	Wed Oct  3 15:33:25 2001
+++ hesiod-3.0.2/hesservbyname.c	Wed Oct  3 15:33:22 2001
@@ -188,7 +188,7 @@
 
 static int cistrcmp(const char *s1, const char *s2)
 {
-  while (*s1 && tolower(*s1) == tolower(*s2))
+  while (*s1 && *s2 && tolower(*s1) == tolower(*s2))
     {
       s1++;
       s2++;