diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/store/audit/HttpReferrerAuditHeader.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/store/audit/HttpReferrerAuditHeader.java
index b2684e758892a..01a36b24fb2f6 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/store/audit/HttpReferrerAuditHeader.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/store/audit/HttpReferrerAuditHeader.java
@@ -29,6 +29,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.StringJoiner;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
@@ -40,6 +41,7 @@
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.fs.audit.CommonAuditContext;
 import org.apache.hadoop.fs.store.LogExactlyOnce;
+import org.apache.hadoop.thirdparty.com.google.common.collect.ImmutableSet;
 import org.apache.http.NameValuePair;
 import org.apache.http.client.utils.URLEncodedUtils;
 
@@ -57,6 +59,13 @@
  * {@code org.apache.hadoop.fs.s3a.audit.TestHttpReferrerAuditHeader}
  * so as to verify that header generation in the S3A auditors, and
  * S3 log parsing, all work.
+ * <p>
+ * This header may be shared across multiple threads at the same time.
+ * so some methods are marked as synchronized, specifically those reading
+ * or writing the attribute map.
+ * <p>
+ * For the same reason, maps and lists passed down during construction are
+ * copied into thread safe structures.
  */
 @InterfaceAudience.Private
 @InterfaceStability.Unstable
@@ -81,6 +90,14 @@ public final class HttpReferrerAuditHeader {
   private static final LogExactlyOnce WARN_OF_URL_CREATION =
       new LogExactlyOnce(LOG);
 
+  /**
+   * Log for warning of an exception raised when building
+   * the referrer header, including building the evaluated
+   * attributes.
+   */
+  private static final LogExactlyOnce ERROR_BUILDING_REFERRER_HEADER =
+      new LogExactlyOnce(LOG);
+
   /** Context ID. */
   private final String contextId;
 
@@ -122,7 +139,11 @@ public final class HttpReferrerAuditHeader {
 
   /**
    * Instantiate.
-   *
+   * <p>
+   * All maps/enums passed down are copied into thread safe equivalents.
+   * as their origin is unknown and cannot be guaranteed to
+   * not be shared.
+   * <p>
    * Context and operationId are expected to be well formed
    * numeric/hex strings, at least adequate to be
    * used as individual path elements in a URL.
@@ -130,15 +151,15 @@ public final class HttpReferrerAuditHeader {
   private HttpReferrerAuditHeader(
       final Builder builder) {
     this.contextId = requireNonNull(builder.contextId);
-    this.evaluated = builder.evaluated;
-    this.filter = builder.filter;
+    this.evaluated = new ConcurrentHashMap<>(builder.evaluated);
+    this.filter = ImmutableSet.copyOf(builder.filter);
     this.operationName = requireNonNull(builder.operationName);
     this.path1 = builder.path1;
     this.path2 = builder.path2;
     this.spanId = requireNonNull(builder.spanId);
 
     // copy the parameters from the builder and extend
-    attributes = builder.attributes;
+    attributes = new ConcurrentHashMap<>(builder.attributes);
 
     addAttribute(PARAM_OP, operationName);
     addAttribute(PARAM_PATH, path1);
@@ -166,17 +187,18 @@ private HttpReferrerAuditHeader(
    * per entry, and "" returned.
    * @return a referrer string or ""
    */
-  public String buildHttpReferrer() {
+  public synchronized String buildHttpReferrer() {
 
     String header;
     try {
+      Map<String, String> requestAttrs = new HashMap<>(attributes);
       String queries;
       // Update any params which are dynamically evaluated
       evaluated.forEach((key, eval) ->
-          addAttribute(key, eval.get()));
+          requestAttrs.put(key, eval.get()));
       // now build the query parameters from all attributes, static and
       // evaluated, stripping out any from the filter
-      queries = attributes.entrySet().stream()
+      queries = requestAttrs.entrySet().stream()
           .filter(e -> !filter.contains(e.getKey()))
           .map(e -> e.getKey() + "=" + e.getValue())
           .collect(Collectors.joining("&"));
@@ -189,7 +211,14 @@ public String buildHttpReferrer() {
     } catch (URISyntaxException e) {
       WARN_OF_URL_CREATION.warn("Failed to build URI for auditor: " + e, e);
       header = "";
+    } catch (RuntimeException e) {
+      // do not let failure to build the header stop the request being
+      // issued.
+      ERROR_BUILDING_REFERRER_HEADER.warn("Failed to construct referred header {}", e.toString());
+      LOG.debug("Full stack", e);
+      header = "";
     }
+
     return header;
   }
 
@@ -200,7 +229,7 @@ public String buildHttpReferrer() {
    * @param key query key
    * @param value query value
    */
-  private void addAttribute(String key,
+  private synchronized void addAttribute(String key,
       String value) {
     if (StringUtils.isNotEmpty(value)) {
       attributes.put(key, value);
diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/ActiveAuditManagerS3A.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/ActiveAuditManagerS3A.java
index 9dd04af68e8a9..e8e989efaa141 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/ActiveAuditManagerS3A.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/ActiveAuditManagerS3A.java
@@ -700,7 +700,8 @@ public SdkResponse modifyResponse(Context.ModifyResponse context,
    * span is deactivated.
    * Package-private for testing.
    */
-  private final class WrappingAuditSpan extends AbstractAuditSpanImpl {
+  @VisibleForTesting
+  final class WrappingAuditSpan extends AbstractAuditSpanImpl {
 
     /**
      * Inner span.
@@ -792,6 +793,15 @@ public boolean isValidSpan() {
       return isValid && span.isValidSpan();
     }
 
+    /**
+     * Get the inner span.
+     * @return the span.
+     */
+    @VisibleForTesting
+    AuditSpanS3A getSpan() {
+      return span;
+    }
+
     /**
      * Forward to the inner span.
      * {@inheritDoc}
diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/LoggingAuditor.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/LoggingAuditor.java
index 5f93454795a94..16bae4b816457 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/LoggingAuditor.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/audit/impl/LoggingAuditor.java
@@ -38,6 +38,7 @@
 import org.slf4j.LoggerFactory;
 
 import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.VisibleForTesting;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.audit.AuditConstants;
 import org.apache.hadoop.fs.audit.CommonAuditContext;
@@ -252,6 +253,17 @@ private void setLastHeader(final String lastHeader) {
     this.lastHeader = lastHeader;
   }
 
+  /**
+   * Get the referrer provided the span is an instance or
+   * subclass of LoggingAuditSpan.
+   * @param span span
+   * @return the referrer
+   * @throws ClassCastException if a different span type was passed in
+   */
+  @VisibleForTesting
+  HttpReferrerAuditHeader getReferrer(AuditSpanS3A span) {
+    return ((LoggingAuditSpan) span).getReferrer();
+  }
   /**
    * Span which logs at debug and sets the HTTP referrer on
    * invocations.
@@ -441,10 +453,10 @@ public String toString() {
     }
 
     /**
-     * Get the referrer; visible for tests.
+     * Get the referrer.
      * @return the referrer.
      */
-    HttpReferrerAuditHeader getReferrer() {
+    private HttpReferrerAuditHeader getReferrer() {
       return referrer;
     }
 
diff --git a/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/TestHttpReferrerAuditHeader.java b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/TestHttpReferrerAuditHeader.java
index 1dfa94cc5adaf..43155fe239f79 100644
--- a/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/TestHttpReferrerAuditHeader.java
+++ b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/TestHttpReferrerAuditHeader.java
@@ -24,6 +24,7 @@
 import java.util.Map;
 import java.util.regex.Matcher;
 
+import org.assertj.core.api.Assertions;
 import software.amazon.awssdk.http.SdkHttpRequest;
 import org.junit.Before;
 import org.junit.Test;
@@ -32,6 +33,7 @@
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.s3a.audit.impl.LoggingAuditor;
+import org.apache.hadoop.fs.s3a.audit.impl.ReferrerExtractor;
 import org.apache.hadoop.fs.store.audit.AuditSpan;
 import org.apache.hadoop.fs.audit.CommonAuditContext;
 import org.apache.hadoop.fs.store.audit.HttpReferrerAuditHeader;
@@ -417,4 +419,33 @@ private void expectStrippedField(final String str,
         .describedAs("Stripped <%s>", str)
         .isEqualTo(ex);
   }
-}
\ No newline at end of file
+
+  /**
+   * Verify that exceptions raised when building referrer headers
+   * do not result in failures, just an empty header.
+   */
+  @Test
+  public void testSpanResilience() throws Throwable {
+    final CommonAuditContext auditContext = CommonAuditContext.currentAuditContext();
+    final String failing = "failing";
+    auditContext.put(failing, () -> {
+      throw new RuntimeException("raised");
+    });
+    try {
+      final HttpReferrerAuditHeader referrer = ReferrerExtractor.getReferrer(auditor, span());
+      Assertions.assertThat(referrer.buildHttpReferrer())
+          .describedAs("referrer header")
+          .isBlank();
+      // repeat
+      LOG.info("second attempt: there should be no second warning below");
+      Assertions.assertThat(referrer.buildHttpReferrer())
+          .describedAs("referrer header 2")
+          .isBlank();
+      referrer.buildHttpReferrer();
+    } finally {
+      // critical to remove this so it doesn't interfere with any other
+      // tests
+      auditContext.remove(failing);
+    }
+  }
+}
diff --git a/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/impl/ReferrerExtractor.java b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/impl/ReferrerExtractor.java
new file mode 100644
index 0000000000000..80d6512c976be
--- /dev/null
+++ b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/audit/impl/ReferrerExtractor.java
@@ -0,0 +1,52 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.fs.s3a.audit.impl;
+
+import org.apache.hadoop.fs.s3a.audit.AuditSpanS3A;
+import org.apache.hadoop.fs.store.audit.HttpReferrerAuditHeader;
+
+/**
+ * Extract the referrer from a LoggingAuditor through a package-private
+ * method.
+ */
+public final class ReferrerExtractor {
+
+  private ReferrerExtractor() {
+  }
+
+  /**
+   * Get the referrer provided the span is an instance or
+   * subclass of LoggingAuditSpan.
+   * If wrapped by a {@code WrappingAuditSpan}, it will be extracted.
+   * @param auditor the auditor.
+   * @param span span
+   * @return the referrer
+   * @throws ClassCastException if a different span type was passed in
+   */
+  public static HttpReferrerAuditHeader getReferrer(LoggingAuditor auditor,
+      AuditSpanS3A span) {
+    AuditSpanS3A sp;
+    if (span instanceof ActiveAuditManagerS3A.WrappingAuditSpan) {
+      sp = ((ActiveAuditManagerS3A.WrappingAuditSpan) span).getSpan();
+    } else {
+      sp = span;
+    }
+    return auditor.getReferrer(sp);
+  }
+}