Unable to find the possible suspect using Code Search or find it.
Assigning it to the concern owner from the ICU regressed range and suspecting the following,

Suspected CL#
https://chromium.googlesource.com/chromium/deps/icu/+/ffa4b6704cf5cc9fec9485731f24a05b2ba94bca

@Mike Aizatsky -- Could you please look into the issue, kindly re-assign if this is not related to your change.
Thank You.

I am the author of the fuzzer, i.e. a tool that uncovered a bug. I have nothing to do with the library code.

Removing EditIssue view restrictions from ClusterFuzz filed bugs. If you believe that this issue should still be restricted, please reapply the label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

@aizatsky -- Thank You for the update.

Using Code Search for the file, "decNumber.c" assigning to the concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/deps/icu.git/+/5feb9ad55c4d3609585820244d59a4462632540c

@jshin -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

For more information, please see https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.md.

The link referenced in the description is no longer valid.

(bulk edit)

ClusterFuzz has detected this issue as fixed in range 525156:525174.

Detailed report: https://clusterfuzz.com/testcase?key=5652488129871872

Fuzzer: libFuzzer_icu_number_format_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Integer-overflow
Crash Address: 
Crash State:
  uprv_decNumberFromString_59
  icu_59::DigitList::set
  icu_59::DecimalFormat::subparse
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=397764:398208
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=525156:525174

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5652488129871872

See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.md for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz testcase 5652488129871872 is verified as fixed, so closing issue as verified.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.