diff --git a/docs/changelog/116212.yaml b/docs/changelog/116212.yaml
new file mode 100644
index 0000000000000..7c8756f4054cd
--- /dev/null
+++ b/docs/changelog/116212.yaml
@@ -0,0 +1,6 @@
+pr: 116212
+summary: Handle status code 0 in S3 CMU response
+area: Snapshot/Restore
+type: bug
+issues:
+ - 102294
diff --git a/modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java b/modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java
index 9757d3af861a9..e13cc40dd3e0f 100644
--- a/modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java
+++ b/modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobContainer.java
@@ -897,8 +897,13 @@ public void compareAndExchangeRegister(
         final var clientReference = blobStore.clientReference();
         ActionListener.run(ActionListener.releaseAfter(listener.delegateResponse((delegate, e) -> {
             logger.trace(() -> Strings.format("[%s]: compareAndExchangeRegister failed", key), e);
-            if (e instanceof AmazonS3Exception amazonS3Exception && amazonS3Exception.getStatusCode() == 404) {
-                // an uncaught 404 means that our multipart upload was aborted by a concurrent operation before we could complete it
+            if (e instanceof AmazonS3Exception amazonS3Exception
+                && (amazonS3Exception.getStatusCode() == 404
+                    || amazonS3Exception.getStatusCode() == 0 && "NoSuchUpload".equals(amazonS3Exception.getErrorCode()))) {
+                // An uncaught 404 means that our multipart upload was aborted by a concurrent operation before we could complete it.
+                // Also (rarely) S3 can start processing the request during a concurrent abort and this can result in a 200 OK with an
+                // <Error><Code>NoSuchUpload</Code>... in the response, which the SDK translates to status code 0. Either way, this means
+                // that our write encountered contention:
                 delegate.onResponse(OptionalBytesReference.MISSING);
             } else {
                 delegate.onFailure(e);
diff --git a/test/fixtures/s3-fixture/src/main/java/fixture/s3/S3HttpHandler.java b/test/fixtures/s3-fixture/src/main/java/fixture/s3/S3HttpHandler.java
index eddce6aae298a..56d3454aa5544 100644
--- a/test/fixtures/s3-fixture/src/main/java/fixture/s3/S3HttpHandler.java
+++ b/test/fixtures/s3-fixture/src/main/java/fixture/s3/S3HttpHandler.java
@@ -13,6 +13,7 @@
 import com.sun.net.httpserver.HttpHandler;
 
 import org.elasticsearch.ExceptionsHelper;
+import org.elasticsearch.common.Randomness;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.UUIDs;
 import org.elasticsearch.common.bytes.BytesReference;
@@ -168,7 +169,21 @@ public void handle(final HttpExchange exchange) throws IOException {
                 RestUtils.decodeQueryString(request, request.indexOf('?') + 1, params);
                 final var upload = uploads.remove(params.get("uploadId"));
                 if (upload == null) {
-                    exchange.sendResponseHeaders(RestStatus.NOT_FOUND.getStatus(), -1);
+                    if (Randomness.get().nextBoolean()) {
+                        exchange.sendResponseHeaders(RestStatus.NOT_FOUND.getStatus(), -1);
+                    } else {
+                        byte[] response = ("""
+                            <?xml version="1.0" encoding="UTF-8"?>
+                            <Error>
+                            <Code>NoSuchUpload</Code>
+                            <Message>No such upload</Message>
+                            <RequestId>test-request-id</RequestId>
+                            <HostId>test-host-id</HostId>
+                            </Error>""").getBytes(StandardCharsets.UTF_8);
+                        exchange.getResponseHeaders().add("Content-Type", "application/xml");
+                        exchange.sendResponseHeaders(RestStatus.OK.getStatus(), response.length);
+                        exchange.getResponseBody().write(response);
+                    }
                 } else {
                     final var blobContents = upload.complete(extractPartEtags(Streams.readFully(exchange.getRequestBody())));
                     blobs.put(requestComponents.path, blobContents);
diff --git a/x-pack/plugin/snapshot-repo-test-kit/qa/s3/src/javaRestTest/java/org/elasticsearch/repositories/blobstore/testkit/analyze/S3RepositoryAnalysisRestIT.java b/x-pack/plugin/snapshot-repo-test-kit/qa/s3/src/javaRestTest/java/org/elasticsearch/repositories/blobstore/testkit/analyze/S3RepositoryAnalysisRestIT.java
index 8986cf1059191..c0f2b40f5a10f 100644
--- a/x-pack/plugin/snapshot-repo-test-kit/qa/s3/src/javaRestTest/java/org/elasticsearch/repositories/blobstore/testkit/analyze/S3RepositoryAnalysisRestIT.java
+++ b/x-pack/plugin/snapshot-repo-test-kit/qa/s3/src/javaRestTest/java/org/elasticsearch/repositories/blobstore/testkit/analyze/S3RepositoryAnalysisRestIT.java
@@ -31,13 +31,6 @@ public class S3RepositoryAnalysisRestIT extends AbstractRepositoryAnalysisRestTe
         .setting("s3.client.repo_test_kit.protocol", () -> "http", (n) -> USE_FIXTURE)
         .setting("s3.client.repo_test_kit.endpoint", s3Fixture::getAddress, (n) -> USE_FIXTURE)
         .setting("xpack.security.enabled", "false")
-        // Additional tracing related to investigation into https://github.com/elastic/elasticsearch/issues/102294
-        .setting("logger.org.elasticsearch.repositories.s3", "TRACE")
-        .setting("logger.org.elasticsearch.repositories.blobstore.testkit", "TRACE")
-        .setting("logger.com.amazonaws.request", "DEBUG")
-        .setting("logger.org.apache.http.wire", "DEBUG")
-        // Necessary to permit setting the above two restricted loggers to DEBUG
-        .jvmArg("-Des.insecure_network_trace_enabled=true")
         .build();
 
     @ClassRule