Predator and CL could not provide any possible suspects.
Using Code Search for the file, "cxfa_node.cpp" assigning to concern owner.

Suspecting Commit#
https://pdfium.googlesource.com/pdfium.git/+/a27c752a048ac2b88bc0c9c293917a7a0494d8a2

@thestig -- Could you please look into it issue, kindly re-assign if this not related your changes.
Thank You.

Not sure if my CL is the culprit, but I'll take a look anyway. It's XFA code, so it's not shipped.

The following revision refers to this bug:
  https://pdfium.googlesource.com/pdfium/+/574756152de82613a71bb206d9fd50906e20f817

commit 574756152de82613a71bb206d9fd50906e20f817
Author: Lei Zhang <thestig@chromium.org>
Date: Fri Sep 15 18:38:56 2017

Fix nullptr dereference in XFA_Node::SetScriptContent().

BUG= chromium:763353 

Change-Id: I6ee93f769509326d9af5bbfa1450c90747d6a065
Reviewed-on: https://pdfium-review.googlesource.com/14090
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

[modify] https://crrev.com/574756152de82613a71bb206d9fd50906e20f817/xfa/fxfa/parser/cxfa_node.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/575358051060409d92287fc51b3daf027048d4bd

commit 575358051060409d92287fc51b3daf027048d4bd
Author: pdfium-deps-roller@chromium.org <pdfium-deps-roller@chromium.org>
Date: Fri Sep 15 19:56:59 2017

Roll src/third_party/pdfium/ 12abfd04a..574756152 (1 commit)

https://pdfium.googlesource.com/pdfium.git/+log/12abfd04a42a..574756152de8

$ git log 12abfd04a..574756152 --date=short --no-merges --format='%ad %ae %s'
2017-09-14 thestig Fix nullptr dereference in XFA_Node::SetScriptContent().

Created with:
  roll-dep src/third_party/pdfium
BUG= 763353 


Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, see:
http://www.chromium.org/developers/tree-sheriffs/sheriff-details-chromium#TOC-Failures-due-to-DEPS-rolls


TBR=dsinclair@chromium.org

Change-Id: Icb93a728624d1f437c006e2b1a9b759db441adc3
Reviewed-on: https://chromium-review.googlesource.com/669138
Reviewed-by: <pdfium-deps-roller@chromium.org>
Commit-Queue: <pdfium-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502336}
[modify] https://crrev.com/575358051060409d92287fc51b3daf027048d4bd/DEPS

ClusterFuzz has detected this issue as fixed in range 502268:502343.

Detailed report: https://clusterfuzz.com/testcase?key=5394433565786112

Fuzzer: libFuzzer_pdfium_xfa_fuzzer
Job Type: libfuzzer_chrome_asan
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000040
Crash State:
  CXFA_Node::GetNodeItem
  CXFA_Node::SetScriptContent
  CXFA_Node::Script_Som_DefaultValue
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan&range=459132:459191
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan&range=502268:502343

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5394433565786112

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 5394433565786112 is verified as fixed, so closing issue as verified.

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