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

Suspect CL: https://chromium.googlesource.com/chromium/deps/icu.git/+/b31896655a701874d13e70cc24bca95e3e66a991

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


Thank You.

 Issue 796811  has been merged into this issue.

 Issue 642853  has been merged into this issue.

 Issue 667049  has been merged into this issue.

From  bug 642853 :

Line 630 of decNumber.c ( https://cs.chromium.org/chromium/src/third_party/icu/source/i18n/decNumber.c?rcl=0&l=630 ) 

has an 'undefined behavior' because X10(e) is expanded to |(e<<3) + (e<<1)| for e >= (2^31-1 / 8). 

The author of the code lets it overflow intentionally. See lines 636 ~ 638. [1] 

    626       for (; *c=='0' && *(c+1)!='\0';) c++;  /* strip insignificant zeros  */
    627       firstexp=c;                            /* save exponent digit place  */
    628       for (; ;c++) {
    629         if (*c<'0' || *c>'9') break;         /* not a digit  */
    630         exponent=X10(exponent)+(Int)*c-(Int)'0';
    631         } /* c  */
    632       /* if not now on a '\0', *c must not be a digit  */
    633       if (*c!='\0') break;
    634 
    635       /* (this next test must be after the syntax checks)  */
    636       /* if it was too long the exponent may have wrapped, so check  */
    637       /* carefully and set it to a certain overflow if wrap possible  */
    638       if (c>=firstexp+9+1) {
    639         if (c>firstexp+9+1 || *firstexp>'1') exponent=DECNUMMAXE*2;
    640         /* [up to 1999999999 is OK, for example 1E-1000000998]  */
    641         }
    642       if (nege) exponent=-exponent;     /* was negative  */
    643       status=0;                         /* is OK  */
    644       } /* stuff after digits  */

Lines 136 ~ 142 have ( https://cs.chromium.org/chromium/src/third_party/icu/source/i18n/decNumber.c?rcl=0&l=136 ) :

    136 /* 4. Exponent checking is minimized by allowing the exponent to      */
    137 /*    grow outside its limits during calculations, provided that      */
    138 /*    the decFinalize function is called later.  Multiplication and   */
    139 /*    division, and intermediate calculations in exponentiation,      */
    140 /*    require more careful checks because of the risk of 31-bit       */
    141 /*    overflow (the most negative valid exponent is -1999999997, for  */
    142 /*    a 999999999-digit number with adjusted exponent of -999999999). */

-------------------------

I wonder if something similar to http://bugs.icu-project.org/trac/changeset/38782 (casting) would work for ubsan. 

Filed an upstream bug at 
http://bugs.icu-project.org/trac/ticket/13550 . 

The upstream may rewrite the part in question before long. 

An upstream has a 2-line fix (int => uint). 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/deps/icu.git/+/aff99f5c22aded55ee29753ce049e61570294967

commit aff99f5c22aded55ee29753ce049e61570294967
Author: Jungshik Shin <jshin@chromium.org>
Date: Thu Apr 12 20:51:41 2018

Cherry pick 3 patches from the upstream

* Fix the undefined behavior in decimal number parsing

      http://bugs.icu-project.org/trac/changeset/40950

* Fix the handling of non-BMP characters in CJK breakiterator

      http://www.icu-project.org/trac/changeset/40949

* Limit the recursion depth of UnicodeSet pattern

      http://bugs.icu-project.org/trac/changeset/40979

TBR=inferno@chromium.org
Bug:  chromium:799850 ,  chromium:796807 ,  chromium:796752 
Test: See the bugs.
Change-Id: I1a8909371b601f36faca911039b10d36c7a92c85
Reviewed-on: https://chromium-review.googlesource.com/1009001
Reviewed-by: Jungshik Shin <jshin@chromium.org>

[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/README.chromium
[add] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/patches/cjkdict_nonbmp.patch
[add] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/patches/number_ub.patch
[add] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/patches/uset_depth.patch
[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/source/common/dictbe.cpp
[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/source/common/unicode/uniset.h
[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/source/common/uniset_closure.cpp
[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/source/common/uniset_props.cpp
[modify] https://crrev.com/aff99f5c22aded55ee29753ce049e61570294967/source/i18n/decNumber.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bcb59cd6dd0e451d00d47b3d4a42a146dd307add

commit bcb59cd6dd0e451d00d47b3d4a42a146dd307add
Author: Jungshik Shin <jshin@chromium.org>
Date: Fri Apr 13 00:33:00 2018

Roll ICU to aff99f5

There are two changes:

 https://chromium.googlesource.com/chromium/deps/icu.git/+log/d888fd2..aff99f5

$ git log d888fd2..aff99f5 --date=short --no-merges --format='%ad %ae %s'
  2018-04-11 jshin@chromium.org Cherry pick 3 patches from the upstream
  2018-04-10 jshin@chromium.org Update IANA tzdb to 2018d and apply a fix
                                for long word selection

TBR=mark@chromium.org,inferno@chromium.org

Bug:  chromium:799850 ,  chromium:796807 ,  chromium:796752 
Bug: chromium:829144, chromium:473288
Test: See the two ICU cls above.
Change-Id: I0adf27e01c0349bd00d4916567bdc0bc70483439
Reviewed-on: https://chromium-review.googlesource.com/1011238
Reviewed-by: Jungshik Shin <jshin@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550435}
[modify] https://crrev.com/bcb59cd6dd0e451d00d47b3d4a42a146dd307add/DEPS

ClusterFuzz has detected this issue as fixed in range 550416:550448.

Detailed report: https://clusterfuzz.com/testcase?key=5042115544612864

Fuzzer: libFuzzer_icu_number_format_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Integer-overflow
Crash Address: 
Crash State:
  uprv_decNumberFromString_60
  icu_60::DigitList::set
  icu_60::DecimalFormat::subparse
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=525422:525449
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=550416:550448

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5042115544612864

See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.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 5042115544612864 is verified as fixed, so closing issue as verified.

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bcb59cd6dd0e451d00d47b3d4a42a146dd307add

commit bcb59cd6dd0e451d00d47b3d4a42a146dd307add
Author: Jungshik Shin <jshin@chromium.org>
Date: Fri Apr 13 00:33:00 2018

Roll ICU to aff99f5

There are two changes:

 https://chromium.googlesource.com/chromium/deps/icu.git/+log/d888fd2..aff99f5

$ git log d888fd2..aff99f5 --date=short --no-merges --format='%ad %ae %s'
  2018-04-11 jshin@chromium.org Cherry pick 3 patches from the upstream
  2018-04-10 jshin@chromium.org Update IANA tzdb to 2018d and apply a fix
                                for long word selection

TBR=mark@chromium.org,inferno@chromium.org

Bug:  chromium:799850 ,  chromium:796807 ,  chromium:796752 
Bug: chromium:829144, chromium:473288
Test: See the two ICU cls above.
Change-Id: I0adf27e01c0349bd00d4916567bdc0bc70483439
Reviewed-on: https://chromium-review.googlesource.com/1011238
Reviewed-by: Jungshik Shin <jshin@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550435}
[modify] https://crrev.com/bcb59cd6dd0e451d00d47b3d4a42a146dd307add/DEPS

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chrome/tools/buildspec/+/82e8c77b1e704e509f1a8aefa4f5e3380943405d

commit 82e8c77b1e704e509f1a8aefa4f5e3380943405d
Author: Jungshik Shin <jungshik@google.com>
Date: Wed Apr 25 16:57:19 2018