1 files changed, 8 insertions, 0 deletions
diff --git a/lib/render/escape.ml b/lib/render/escape.ml
index 53fdd46..f506c44 100644
--- a/lib/render/escape.ml
+++ b/lib/render/escape.ml
@@ -77,6 +77,14 @@ let fold_ics line =
     else begin
       let cut = ref (pos + limit) in
       while !cut > pos && is_cont line.[!cut] do decr cut done;
+      (* Valid UTF-8's longest continuation run is 3, so backoff finds a
+         boundary within a few bytes. But this function must stay TOTAL on
+         ARBITRARY octet strings, not only valid UTF-8: 74+ consecutive
+         continuation bytes back `cut` all the way down to `pos`, which would
+         yield a zero-length chunk and recurse on the identical position
+         forever. When backoff finds no boundary inside the window, cut hard
+         at the limit instead -- forward progress is then unconditional. *)
+      if !cut = pos then cut := pos + limit;
       if not first then Buffer.add_char b ' ';
       Buffer.add_string b (String.sub line pos (!cut - pos));
       Buffer.add_string b "\r\n";