Predator and CL did not provide any possible suspects.
Using Code Search for the file, "agg_render_scanlines.h" adding few concern owners from GitBlame.
Suspecting Commit#
https://pdfium.googlesource.com/pdfium.git/+/5110c4743751145c4ae1934cd1d83bc6c55bb43f

Could some one please look into the issue and update.
Thank You.

ClusterFuzz has detected this issue as fixed in range 465098:465130.

Detailed report: https://clusterfuzz.com/testcase?key=5180774300254208

Fuzzer: libfuzzer_pdfium_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Undefined-shift
Crash Address: 
Crash State:
  bool agg::rasterizer_scanline_aa::sweep_scanline<agg::scanline_u<unsigned char> 
  void agg::render_scanlines<agg::rasterizer_scanline_aa, agg::scanline_u<unsigned
  CFX_AggDeviceDriver::SetClipMask
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=465081:465098
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=465098:465130

Reproducer Testcase: https://clusterfuzz.com/download/AMIfv95Vx7ssQDq0jAFWVTf8Lw4yJGr-CJu8_bEoqOdGpAMAhoiIL6kKpt5ZX-rLRvsJukuAtf6Z1Bz-0osGz9f1Sru_rabJBv9d2gW7d62evyRTmnauWtLDaJByuHI_Ve2NmYE82qqKYDdVlhDm1dh_Lvo-yeKdpwdJ_5T_ckFIvqR9484xrsXx8Hx3lxJrEgHOdC3vZf4hVoROeyZSxXTIqoFpn9LKBkRU6kx0DgFlXcpyTTs_Ck6hvTDUTNE06XqT-NeLtDp9VDz0V3G89hWetjFN1fJyTNDOzFSXxXNaBRxSiIM9rrIkpeTlPdC0YT-GBxWaDFmyP_ICoLk4_UvNmxjNhjZa9BEC7wPzA2g0hU0wsSR2tcY?testcase_id=5180774300254208


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 5180774300254208 is verified as fixed, so closing issue.

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

We should verify this is fixed.

Bulk-WontFixing these bugs. This was a bug on ClusterFuzz side, see bug 717534. We will start seeing new testcases auto-filed in a day or two. We can't leave these open as ClusterFuzz won't autoverify them after ClusterFuzz-Wrong label.

We have made a bunch of changes on ClusterFuzz side, so resetting ClusterFuzz-Wrong label.