From ae7819ddb1a105004a8d2d6e0af56cba65968b65 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Wed, 6 Apr 2022 17:52:09 +0100
Subject: [PATCH] Fix for numeric overflow found during fuzzing.

---
 include/boost/regex/v5/basic_regex_creator.hpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/boost/regex/v5/basic_regex_creator.hpp b/include/boost/regex/v5/basic_regex_creator.hpp
index 82306d36..bb76c7c1 100644
--- a/include/boost/regex/v5/basic_regex_creator.hpp
+++ b/include/boost/regex/v5/basic_regex_creator.hpp
@@ -1019,6 +1019,8 @@ int basic_regex_creator<charT, traits>::calculate_backstep(re_syntax_base* state
             {
                if(rep->max != rep->min)
                   return -1;
+               if (static_cast<std::size_t>((std::numeric_limits<int>::max)() - result) < rep->min)
+                  return -1; // protection against overflow, we can't calculate a backstep in this case and the expression is probably ill-formed.
                result += static_cast<int>(rep->min);
                state = rep->alt.p;
                continue;