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mruby-regexp: fix a heap-buffer-overflow read in MatchData#[] for an over-long group name #7002

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Merged
matz merged 1 commit into from
Aug 3, 2026
Merged

mruby-regexp: fix a heap-buffer-overflow read in MatchData#[] for an over-long group name #7002

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5 changes: 4 additions & 1 deletion mrbgems/mruby-regexp/src/regexp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -592,7 +592,10 @@ matchdata_aref(mrb_state *mrb, mrb_value self)
if (!mrb_nil_p(md->regexp)) {
pat = DATA_GET_PTR(mrb, md->regexp, &regexp_type, mrb_regexp_pattern);
}
if (pat) {
/* A stored name never exceeds UINT16_MAX, so a longer request can name no
group. Rejecting it here keeps the cast in the loop lossless; without it
the length test truncates while the memcmp() next to it does not. */
if (pat && name_len <= UINT16_MAX) {
for (uint16_t i = 0; i < pat->num_named; i++) {
if (pat->named_captures[i].name_len == (uint16_t)name_len &&
memcmp(pat->named_captures[i].name, name, name_len) == 0) {
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10 changes: 10 additions & 0 deletions mrbgems/mruby-regexp/test/regexp.rb
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Expand Up @@ -1076,6 +1076,16 @@ def limit.to_int; 1.5; end
assert_raise(IndexError) { /(a)/.match("a")[:zz] }
end

assert("MatchData#[] - group name longer than a uint16 length") do
# Regression: the length test truncated the requested length to uint16_t
# while the memcmp() next to it did not, so (uint16_t)65539 == 3 ==
# "abc".length let a 65539-byte read run off a 3-byte arena. The result is
# unchanged either way; only a sanitizer build fails on it.
md = /(?<abc>x)/.match("x")
assert_raise(IndexError) { md["abc" + "A" * 65536] }
assert_equal "x", md[:abc]
end

assert("Regexp - named backreference \\k") do
assert_equal "aa", "aa".match(/(?<n>\w)\k<n>/)[0]
assert_equal "abba", "abba".match(/(?<a>.)(?<b>.)\k<b>\k<a>/)[0]
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