diff --git a/src/clusterfuzz/_internal/bot/tasks/utasks/progression_task.py b/src/clusterfuzz/_internal/bot/tasks/utasks/progression_task.py
index 24cd3bb479..f7f770aefd 100644
--- a/src/clusterfuzz/_internal/bot/tasks/utasks/progression_task.py
+++ b/src/clusterfuzz/_internal/bot/tasks/utasks/progression_task.py
@@ -246,6 +246,40 @@ def _write_to_bigquery(testcase, progression_range_start,
       end=progression_range_end)
 
 
+_FATAL_EXECUTION_RETURN_CODES = frozenset({126, 127})
+_FATAL_LINKER_MARKERS = (
+    'error while loading shared libraries:',
+    'cannot open shared object file',
+)
+_ABI_VERSION_TOKENS = ('GLIBC_', 'GLIBCXX_', 'CXXABI_')
+
+
+def _is_fatal_execution_or_linker_failure(crash_result) -> bool:
+  """Returns True if execution failed due to OS loader / library errors."""
+  if crash_result is None:
+    return False
+
+  return_code = getattr(crash_result, 'return_code', None)
+  if isinstance(return_code, int) and not isinstance(
+      return_code, bool) and return_code in _FATAL_EXECUTION_RETURN_CODES:
+    return True
+
+  candidate_outputs = [getattr(crash_result, 'output', None)]
+  if hasattr(crash_result, 'get_stacktrace'):
+    candidate_outputs.append(crash_result.get_stacktrace(symbolized=False))
+
+  for text in candidate_outputs:
+    if not isinstance(text, str) or not text:
+      continue
+    if 'not found' in text and any(
+        token in text for token in _ABI_VERSION_TOKENS):
+      return True
+    if any(marker in text for marker in _FATAL_LINKER_MARKERS):
+      return True
+
+  return False
+
+
 def _log_output(revision, crash_result):
   """Log process output."""
   logs.info(
@@ -280,6 +314,16 @@ def _check_fixed_for_custom_binary(testcase: data_types.Testcase,
       http_flag=testcase.http_flag)
   _log_output(revision, result)
 
+  if _is_fatal_execution_or_linker_failure(result):
+    error_message = (
+        f'Target execution failed with loader error '
+        f'(code={result.return_code}) on custom build r{revision}.')
+    logs.error(error_message)
+    return uworker_msg_pb2.Output(  # pylint: disable=no-member
+        progression_task_output=uworker_msg_pb2.ProgressionTaskOutput(),  # pylint: disable=no-member
+        error_message=error_message,
+        error_type=uworker_msg_pb2.ErrorType.PROGRESSION_BAD_BUILD)  # pylint: disable=no-member
+
   # If this still crashes on the most recent build, it's not fixed. The task
   # will be rescheduled by a cron job and re-attempted eventually.
   if result.is_crash():
@@ -369,6 +413,15 @@ def _testcase_reproduces_in_revision(
       test_timeout,
       http_flag=testcase.http_flag)
   _log_output(revision, result)
+  if _is_fatal_execution_or_linker_failure(result):
+    progression_task_output.build_data_list[-1].is_bad_build = True
+    error_message = (f'Target execution failed with loader error '
+                     f'(code={result.return_code}) at r{revision}. Skipping')
+    logs.error(error_message)
+    return None, uworker_msg_pb2.Output(  # pylint: disable=no-member
+        progression_task_output=progression_task_output,
+        error_message=error_message,
+        error_type=uworker_msg_pb2.ErrorType.PROGRESSION_BAD_BUILD)  # pylint: disable=no-member
   return result, None
 
 
diff --git a/src/clusterfuzz/_internal/tests/core/bot/tasks/utasks/progression_task_test.py b/src/clusterfuzz/_internal/tests/core/bot/tasks/utasks/progression_task_test.py
index 09057af9a1..a9d89512a6 100644
--- a/src/clusterfuzz/_internal/tests/core/bot/tasks/utasks/progression_task_test.py
+++ b/src/clusterfuzz/_internal/tests/core/bot/tasks/utasks/progression_task_test.py
@@ -71,6 +71,7 @@ def setUp(self):
     ])
     helpers.patch_environ(self)
     os.environ['APP_NAME'] = 'app_name'
+    os.environ['CONFIG_DIR_OVERRIDE'] = './configs/test'
 
   def test_error_on_failed_setup(self):
     """Ensure that we throw an exception if we fail to set up a build."""
@@ -120,6 +121,52 @@ def test_no_crash(self):
     self.assertEqual(len(progression_task_output.build_data_list), 1)
     self.assertEqual(progression_task_output.build_data_list[0], build_data)
 
+  def test_exit_127_missing_shared_library_treated_as_bad_build(self):
+    """Ensures exit 126/127 or missing .so aborts as PROGRESSION_BAD_BUILD."""
+    from clusterfuzz._internal.crash_analysis.crash_result import \
+        CrashResult  # pylint: disable=import-outside-toplevel
+    build_data = uworker_msg_pb2.BuildData(
+        revision=42,
+        is_bad_build=False,
+        should_ignore_crash_result=False,
+        build_run_console_output='')
+    self.mock.check_for_bad_build.return_value = build_data
+    self.mock.test_for_crash_with_retries.return_value = CrashResult(
+        127, 0.1,
+        '/out/fuzzer: error while loading shared libraries: libssl.so.1.1: '
+        'cannot open shared object file: No such file or directory')
+    testcase = data_types.Testcase()
+    progression_task_output = uworker_msg_pb2.ProgressionTaskOutput()
+    result, worker_output = progression_task._testcase_reproduces_in_revision(  # pylint: disable=protected-access
+        testcase, '/tmp/blah', 'job_type', 42, None, progression_task_output)
+    self.assertIsNone(result)
+    self.assertIsNotNone(worker_output)
+    self.assertEqual(worker_output.error_type,
+                     uworker_msg_pb2.ErrorType.PROGRESSION_BAD_BUILD)
+    self.assertTrue(progression_task_output.build_data_list[0].is_bad_build)
+
+  def test_glibc_symbol_mismatch_with_zero_return_code_treated_as_bad_build(
+      self):
+    """Ensures ABI errors abort even after reproduce_with_retries sets 0."""
+    from clusterfuzz._internal.crash_analysis.crash_result import \
+        CrashResult  # pylint: disable=import-outside-toplevel
+    build_data = uworker_msg_pb2.BuildData(
+        revision=43,
+        is_bad_build=False,
+        should_ignore_crash_result=False,
+        build_run_console_output='')
+    self.mock.check_for_bad_build.return_value = build_data
+    self.mock.test_for_crash_with_retries.return_value = CrashResult(
+        0, 0, '/out/fuzzer: /lib/x86_64-linux-gnu/libc.so.6: '
+        "version `GLIBC_2.38' not found")
+    testcase = data_types.Testcase()
+    progression_task_output = uworker_msg_pb2.ProgressionTaskOutput()
+    result, worker_output = progression_task._testcase_reproduces_in_revision(  # pylint: disable=protected-access
+        testcase, '/tmp/blah', 'job_type', 43, None, progression_task_output)
+    self.assertIsNone(result)
+    self.assertEqual(worker_output.error_type,
+                     uworker_msg_pb2.ErrorType.PROGRESSION_BAD_BUILD)
+
 
 @test_utils.with_cloud_emulators('datastore')
 class UtaskPreprocessTest(unittest.TestCase):