The problem is at
CJPX_Decoder::Init(unsigned char const*, unsigned int) third_party/pdfium/core/fxcodec/codec/fx_codec_jpx_opj.cpp:773

Oliver, do you have time to take a look at this? If not, feel free to assign back.

Sorry, don't have time for this :(

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

Not sure what the right way to fix this is, and it doesn't seem to be solved upstream. Will take a look later, or anyone feel free to take this.

Filed a bug on github:
https://github.com/uclouvain/openjpeg/issues/885

ClusterFuzz has detected this issue as fixed in range 469455:469504.

Detailed report: https://clusterfuzz.com/testcase?key=4744148382121984

Fuzzer: libfuzzer_pdf_jpx_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Undefined-shift
Crash Address: 
Crash State:
  opj_get_all_encoding_parameters
  opj_pi_create_decode
  opj_t2_decode_packets
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=395640:395746
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=469455:469504

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=4744148382121984


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 4744148382121984 is verified as fixed, so closing issue.

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

Bugdroid forgot to mention this was fixed in https://pdfium.googlesource.com/pdfium/+/34f735c9ef34b3bb6493016c7fbeb6df76cf31f5