Index: head/lib/libc/gen/getgrent.c
===================================================================
--- head/lib/libc/gen/getgrent.c
+++ head/lib/libc/gen/getgrent.c
@@ -334,14 +334,27 @@
 	orig_buf_size = va_arg(ap, size_t);
 	ret_errno = va_arg(ap, int *);
 
-	if (orig_buf_size <
-	    buffer_size - sizeof(struct group) - sizeof(char *)) {
+	if (orig_buf_size + sizeof(struct group) + sizeof(char *) < buffer_size)
+	{
 		*ret_errno = ERANGE;
 		return (NS_RETURN);
+	} else if (buffer_size < sizeof(struct group) + sizeof(char *)) {
+		/*
+		 * nscd(8) sometimes returns buffer_size=1 for nonexistent
+		 * entries.
+		 */
+		*ret_errno = 0;
+		return (NS_NOTFOUND);
 	}
 
 	memcpy(grp, buffer, sizeof(struct group));
 	memcpy(&p, buffer + sizeof(struct group), sizeof(char *));
+
+	if (orig_buf_size + sizeof(struct group) + sizeof(char *) +
+	    _ALIGN(p) - (size_t)p < buffer_size) {
+		*ret_errno = ERANGE;
+		return (NS_RETURN);
+	}
 
 	orig_buf = (char *)_ALIGN(orig_buf);
 	memcpy(orig_buf, buffer + sizeof(struct group) + sizeof(char *) +
Index: head/lib/libc/gen/getpwent.c
===================================================================
--- head/lib/libc/gen/getpwent.c
+++ head/lib/libc/gen/getpwent.c
@@ -389,10 +389,17 @@
 	orig_buf_size = va_arg(ap, size_t);
 	ret_errno = va_arg(ap, int *);
 
-	if (orig_buf_size <
-	    buffer_size - sizeof(struct passwd) - sizeof(char *)) {
+	if (orig_buf_size + sizeof(struct passwd) + sizeof(char *) <
+	    buffer_size) {
 		*ret_errno = ERANGE;
 		return (NS_RETURN);
+	} else if (buffer_size < sizeof(struct passwd) + sizeof(char *)) {
+		/*
+		 * nscd(8) sometimes returns buffer_size=1 for nonexistent
+		 * entries.
+		 */
+		*ret_errno = 0;
+		return (NS_NOTFOUND);
 	}
 
 	memcpy(pwd, buffer, sizeof(struct passwd));