This issue looks similar to  bug 824562 , hence assigning to the same owner for more updates on this issue.

lfg@ Could you please take a look in to this issue?

Thanks!

I think this is a dupe, I asked clusterfuzz to try again to double check that the fix landed also works here.

ClusterFuzz has detected this issue as fixed in range 547798:549174.

Detailed report: https://clusterfuzz.com/testcase?key=5007771595177984

Fuzzer: attekett_dom_fuzzer
Job Type: linux_cfi_chrome
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x0000000004bc
Crash State:
  blink::Document::SetCompatibilityMode
  blink::HTMLTreeBuilder::DefaultForInitial
  blink::HTMLTreeBuilder::ProcessStartTag
  
Sanitizer: cfi (CFI)

Regressed: https://clusterfuzz.com/revisions?job=linux_cfi_chrome&range=536346:536353
Fixed: https://clusterfuzz.com/revisions?job=linux_cfi_chrome&range=547798:549174

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5007771595177984

See https://github.com/google/clusterfuzz-tools 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 5007771595177984 is verified as fixed, so closing issue as verified.

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

Clusterfuzz verified the fix, I'm marking as a dupe so we can track the fix.