This issue is a security regression. If you are not able to fix this quickly, please revert the change that introduced it.

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

The ICU update to 58 is the likely cause of this regression: https://codereview.chromium.org/2442923002

jshin -- Can you take a look?

Or, it can be just an old symptom rediscovered due to an icu symbol change (icu56_foo => icu58_foo). 

Anyway,sorry for the late reply. I'm looking at it. 

Oh... It's BreakIterator. Then, it is likely to be new. Adding aheninger@. 

The API in question for title casing UTF-8 input is not used by Blink/Chrome/v8. 

Moreover, even if it's used, Chrome/v8/Blink would not feed invalid UTF-8 to the API that takes a UTF-8 string as an input, but the minimum test case uses an invalid UTF-8 string. 

Given these, I'm lowering the priority and removing Release-Block-Beta. 

This issue is a security regression. If you are not able to fix this quickly, please revert the change that introduced it.

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

jshin: Uh oh! This issue still open and hasn't been updated in the last 14 days. This is a serious vulnerability, and we want to ensure that there's progress. Could you please leave an update with the current status and any potential blockers?

If you're not the right owner for this issue, could you please remove yourself as soon as possible or help us find the right one?

If the issue is fixed or you can't reproduce it, please close the bug. If you've started working on a fix, please set the status to Started.

Thanks for your time! To disable nags, add the Disable-Nags label.

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

Removing security flags based on #8.

ClusterFuzz has detected this issue as fixed in range 471616:471627.

Detailed report: https://clusterfuzz.com/testcase?key=6356259289956352

Fuzzer: libfuzzer_icu_ucasemap_fuzzer
Job Type: libfuzzer_chrome_msan
Platform Id: linux

Crash Type: Use-of-uninitialized-value
Crash Address: 
Crash State:
  utext_next32_58
  icu_58::RuleBasedBreakIterator::handleNext
  icu_58::RuleBasedBreakIterator::next
  
Sanitizer: memory (MSAN)

Recommended Security Severity: Medium

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_msan&range=429309:429390
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_msan&range=471616:471627

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6356259289956352


See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reproducing.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 6356259289956352 is verified as fixed, so closing issue.

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