diff --git a/format.c b/format.c
index 3456a823d..b29675a97 100644
--- a/format.c
+++ b/format.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: format.c,v 1.421 2026/09/28 16:52:55 nicm Exp $ */
+/* $OpenBSD: format.c,v 1.423 2026/09/29 13:59:10 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -88,9 +88,12 @@ format_job_cmp(struct format_job *fj1, struct format_job *fj2)
 /* Maximum pad and trim width. */
 #define FORMAT_MAX_WIDTH 10000
 
-/* Maximum repeat size. */
+/* Maximum repeat count. */
 #define FORMAT_MAX_REPEAT 10000
 
+/* Maximum repeat result size in bytes. */
+#define FORMAT_MAX_REPEAT_SIZE 65536
+
 /* Maximum precision. */
 #define FORMAT_MAX_PRECISION 100
 
@@ -4520,8 +4523,8 @@ format_pretty_time(time_t t, int seconds)
 		now = t;
 	age = now - t;
 
-	localtime_r(&now, &now_tm);
-	localtime_r(&t, &tm);
+	if (localtime_r(&now, &now_tm) == NULL || localtime_r(&t, &tm) == NULL)
+		return (xstrdup(""));
 
 	/* Last 24 hours. */
 	if (age < 24 * 3600) {
@@ -4692,10 +4695,12 @@ found:
 			found = format_pretty_time(t, 0);
 		else {
 			if (time_format != NULL) {
-				localtime_r(&t, &tm);
+				if (localtime_r(&t, &tm) == NULL)
+					return (NULL);
 				format_strftime(s, sizeof s, time_format, &tm);
 			} else {
-				ctime_r(&t, s);
+				if (ctime_r(&t, s) == NULL)
+					return (NULL);
 				s[strcspn(s, "\n")] = '\0';
 			}
 			found = xstrdup(s);
@@ -6427,7 +6432,7 @@ format_replace(struct format_expand_state *es, const char *key, size_t keylen,
 			value = xstrdup("");
 		else {
 			n = strlen(left);
-			if (n != 0 && nrep > (SIZE_MAX - 1) / n) {
+			if (n != 0 && nrep > FORMAT_MAX_REPEAT_SIZE / n) {
 				format_log(es, "repeat is too long: %s", copy);
 				value = xstrdup("");
 			} else {