commit 385e8759c3ff1e7f7f996bd4ea391074d61d48c1
Author:     Karl Williamson <khw@cpan.org>
AuthorDate: 2024-12-18 18:25:29 -0700
Commit:     Steve Hay <steve.m.hay@googlemail.com>
CommitDate: 2025-03-30 11:59:51 +0100

    CVE-2024-56406: Heap-buffer-overflow with tr//

    This was due to underallocating needed space.  If the translation forces
    something to become UTF-8 that is initially bytes, that UTF-8 could
    now require two bytes where previously a single one would do.

    (cherry picked from commit f93109c8a6950aafbd7488d98e112552033a3686)

diff --git a/op.c b/op.c
index 3fc23eca49a..aeee88e0335 100644
--- a/op.c
+++ b/op.c
@@ -6649,6 +6649,7 @@ S_pmtrans(pTHX_ OP *o, OP *expr, OP *repl)
                  * same time.  But otherwise one crosses before the other */
                 if (t_cp < 256 && r_cp_end > 255 && r_cp != t_cp) {
                     can_force_utf8 = TRUE;
+                    max_expansion = MAX(2, max_expansion);
                 }
             }