Predator and CL could not provide any possible suspects.
Using Code Search for the file, "cxfa_fmparser.cpp" assigning to the concern owner who might be related.

Suspecting Commit#
https://pdfium.googlesource.com/pdfium.git/+/db1e8a500588abb98026bafac376b953f61813d2

Unable to add Author as owner, Hence assigning this issue to Reviewer.

@rharrison -- Could you please look into the issue, kindly re-assign if this is not related to your changes.

Thank You.

The following revision refers to this bug:
  https://pdfium.googlesource.com/pdfium/+/c9d6d68e9b91a0373d8aac42cdde5dac1925ec42

commit c9d6d68e9b91a0373d8aac42cdde5dac1925ec42
Author: Ryan Harrison <rharrison@chromium.org>
Date: Tue Aug 29 18:42:43 2017

Fix incorrectly guarded lexer advancement in FormCalc parser

BUG= chromium:752501 

Change-Id: Ie9943cd80a4afa73ad9393c8bcd2aa2656a9d932
Reviewed-on: https://pdfium-review.googlesource.com/12290
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

[modify] https://crrev.com/c9d6d68e9b91a0373d8aac42cdde5dac1925ec42/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
[modify] https://crrev.com/c9d6d68e9b91a0373d8aac42cdde5dac1925ec42/xfa/fxfa/fm2js/cxfa_fmparser.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/db822bc8390616b59868396f0b3265cc71e6cd16

commit db822bc8390616b59868396f0b3265cc71e6cd16
Author: pdfium-deps-roller@chromium.org <pdfium-deps-roller@chromium.org>
Date: Tue Aug 29 22:11:38 2017

Roll src/third_party/pdfium/ 31f7e4bb5..c9d6d68e9 (1 commit)

https://pdfium.googlesource.com/pdfium.git/+log/31f7e4bb502e..c9d6d68e9b91

$ git log 31f7e4bb5..c9d6d68e9 --date=short --no-merges --format='%ad %ae %s'
2017-08-29 rharrison Fix incorrectly guarded lexer advancement in FormCalc parser

Created with:
  roll-dep src/third_party/pdfium
BUG= 752501 


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: Ifbdaba848ed19930f34bc4c91b623299ace2474e
Reviewed-on: https://chromium-review.googlesource.com/642174
Reviewed-by: <pdfium-deps-roller@chromium.org>
Commit-Queue: <pdfium-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498250}
[modify] https://crrev.com/db822bc8390616b59868396f0b3265cc71e6cd16/DEPS

ClusterFuzz has detected this issue as fixed in range 498213:498262.

Detailed report: https://clusterfuzz.com/testcase?key=6470373762924544

Fuzzer: afl_pdf_fm2js_fuzzer
Job Type: afl_chrome_asan
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000010
Crash State:
  CXFA_FMParser::ParsePostExpression
  CXFA_FMParser::ParsePrimaryExpression
  CXFA_FMParser::ParseUnaryExpression
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=afl_chrome_asan&range=490107:490254
Fixed: https://clusterfuzz.com/revisions?job=afl_chrome_asan&range=498213:498262

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6470373762924544

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 6470373762924544 is verified as fixed, so closing issue as verified.

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