diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index e795cb9dd..687be46c4 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -32,3 +32,8 @@
 **Vulnerability:** The document hashing routine in `DefaultDocumentConversionService` processed file streams without enforcing any maximum size limit on the bytes read. An attacker could exploit this by uploading a maliciously large stream (or exploiting a compression bomb if unzipping), exhausting system memory, CPU, or disk space (DoS).
 **Learning:** Checking the declared file size (e.g., `file.getSize()`) in initial validation is not always sufficient if the input stream itself can be spoofed or dynamically expanded during reading. The actual bytes read must be verified against bounds continuously.
 **Prevention:** Always enforce a strict, configurable size limit (e.g., `ConversionProperties.maxUploadSizeBytes`) within the `while` loop that reads from untrusted input streams. Track `totalRead` and throw an exception immediately if the limit is exceeded.
+
+## 2026-07-23 - Backend API Endpoint Authentication Enforcement
+**Vulnerability:** Admin endpoints (`/api/v1/admin/convert/jobs`) were missing proper authentication and authorization checks, allowing unauthenticated or unauthorized access to sensitive administrative actions like viewing all jobs or deleting jobs.
+**Learning:** All backend API endpoints, especially those dealing with administrative or sensitive actions, must enforce authentication and authorization. Merely having the endpoints defined in a controller without verifying the incoming request context leaves the system open to abuse.
+**Prevention:** Always inject `TenantAccessService` into controllers and invoke `tenantAccessService.require(headers, TenantPermissions.[SPECIFIC_PERMISSION])` (e.g., `ADMIN_READ`, `ADMIN_WRITE`) to ensure that every request to a backend API endpoint is properly authenticated and authorized before processing.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e8e8c9806..5a696db4a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,3 +48,6 @@
 
 ### Fixed
 - 뷰어 UI의 재시도 버튼 로딩 상태가 내부 DOM을 손상시키지 않고 안전하게 복원되도록 수정
+
+### 보안 (Security)
+- 백엔드 관리자 API 엔드포인트에 대한 인증 및 인가(`TenantAccessService`) 적용.
diff --git a/src/main/java/com/clearfolio/viewer/auth/TenantPermissions.java b/src/main/java/com/clearfolio/viewer/auth/TenantPermissions.java
index ced5e6a3d..fcc0d4b5a 100644
--- a/src/main/java/com/clearfolio/viewer/auth/TenantPermissions.java
+++ b/src/main/java/com/clearfolio/viewer/auth/TenantPermissions.java
@@ -50,6 +50,16 @@ public final class TenantPermissions {
      */
     public static final String ANALYTICS_READ = "analytics:read";
 
+    /**
+     * Permission required to read admin resources.
+     */
+    public static final String ADMIN_READ = "admin:read";
+
+    /**
+     * Permission required to write admin resources.
+     */
+    public static final String ADMIN_WRITE = "admin:write";
+
     private TenantPermissions() {
     }
 }
diff --git a/src/main/java/com/clearfolio/viewer/controller/AdminController.java b/src/main/java/com/clearfolio/viewer/controller/AdminController.java
index 412d4eb86..add8dc9e6 100644
--- a/src/main/java/com/clearfolio/viewer/controller/AdminController.java
+++ b/src/main/java/com/clearfolio/viewer/controller/AdminController.java
@@ -4,17 +4,21 @@
 import java.util.List;
 import java.util.UUID;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.server.ResponseStatusException;
 
 import com.clearfolio.viewer.api.AdminJobListResponse;
+import com.clearfolio.viewer.auth.TenantAccessService;
+import com.clearfolio.viewer.auth.TenantPermissions;
 import com.clearfolio.viewer.model.ConversionJob;
 import com.clearfolio.viewer.service.DocumentConversionService;
 import com.clearfolio.viewer.service.RetryDeadLetterResult;
@@ -26,14 +30,17 @@
 public class AdminController {
 
     private final DocumentConversionService conversionService;
+    private final TenantAccessService tenantAccessService;
 
     /**
      * Creates a controller for admin operations.
      *
      * @param conversionService conversion service
+     * @param tenantAccessService tenant access service
      */
-    public AdminController(DocumentConversionService conversionService) {
+    public AdminController(DocumentConversionService conversionService, TenantAccessService tenantAccessService) {
         this.conversionService = conversionService;
+        this.tenantAccessService = tenantAccessService;
     }
 
     /**
@@ -43,7 +50,11 @@ public AdminController(DocumentConversionService conversionService) {
      * @return list of conversion jobs
      */
     @GetMapping("/api/v1/admin/convert/jobs")
-    public AdminJobListResponse getAllJobs(@RequestParam(required = false) Boolean deadLettered) {
+    public AdminJobListResponse getAllJobs(
+            @RequestParam(required = false) Boolean deadLettered,
+            @RequestHeader HttpHeaders headers) {
+        tenantAccessService.require(headers, TenantPermissions.ADMIN_READ);
+
         Iterable<ConversionJob> allJobs = conversionService.getAllJobs();
 
         if (deadLettered == null) {
@@ -66,7 +77,11 @@ public AdminJobListResponse getAllJobs(@RequestParam(required = false) Boolean d
      * @return no content on success
      */
     @DeleteMapping("/api/v1/admin/convert/jobs/{jobId}")
-    public ResponseEntity<Void> deleteJob(@PathVariable UUID jobId) {
+    public ResponseEntity<Void> deleteJob(
+            @PathVariable UUID jobId,
+            @RequestHeader HttpHeaders headers) {
+        tenantAccessService.require(headers, TenantPermissions.ADMIN_WRITE);
+
         conversionService.deleteJob(jobId);
         return ResponseEntity.noContent().build();
     }
@@ -78,7 +93,11 @@ public ResponseEntity<Void> deleteJob(@PathVariable UUID jobId) {
      * @return accepted response on success
      */
     @PostMapping("/api/v1/admin/convert/jobs/{jobId}/retry")
-    public ResponseEntity<Void> retryDeadLettered(@PathVariable UUID jobId) {
+    public ResponseEntity<Void> retryDeadLettered(
+            @PathVariable UUID jobId,
+            @RequestHeader HttpHeaders headers) {
+        tenantAccessService.require(headers, TenantPermissions.ADMIN_WRITE);
+
         RetryDeadLetterResult result = conversionService.retryDeadLettered(jobId, "admin");
         if (result == RetryDeadLetterResult.NOT_FOUND) {
             throw new ResponseStatusException(HttpStatus.NOT_FOUND, "job not found");
diff --git a/src/test/java/com/clearfolio/viewer/controller/AdminControllerTest.java b/src/test/java/com/clearfolio/viewer/controller/AdminControllerTest.java
index ad63a8015..f2603f284 100644
--- a/src/test/java/com/clearfolio/viewer/controller/AdminControllerTest.java
+++ b/src/test/java/com/clearfolio/viewer/controller/AdminControllerTest.java
@@ -10,6 +10,7 @@
 import org.junit.jupiter.api.Test;
 import org.springframework.test.web.reactive.server.WebTestClient;
 
+import com.clearfolio.viewer.auth.TenantAccessService;
 import com.clearfolio.viewer.model.ConversionJob;
 import com.clearfolio.viewer.service.DocumentConversionService;
 import com.clearfolio.viewer.service.RetryDeadLetterResult;
@@ -17,13 +18,15 @@
 class AdminControllerTest {
 
     private DocumentConversionService conversionService;
+    private TenantAccessService tenantAccessService;
     private WebTestClient webTestClient;
     private AdminController controller;
 
     @BeforeEach
     void setUp() {
         conversionService = mock(DocumentConversionService.class);
-        controller = new AdminController(conversionService);
+        tenantAccessService = mock(TenantAccessService.class);
+        controller = new AdminController(conversionService, tenantAccessService);
         webTestClient = WebTestClient.bindToController(controller)
                 .controllerAdvice(new ApiExceptionHandler())
                 .build();
@@ -37,6 +40,7 @@ void getAllJobsReturnsAllJobsWhenNoFilterProvided() {
 
         webTestClient.get()
                 .uri("/api/v1/admin/convert/jobs")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isOk()
                 .expectBody()
@@ -55,6 +59,7 @@ void getAllJobsFiltersByDeadLetteredTrue() {
 
         webTestClient.get()
                 .uri("/api/v1/admin/convert/jobs?deadLettered=true")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isOk()
                 .expectBody()
@@ -72,6 +77,7 @@ void getAllJobsFiltersByDeadLetteredFalse() {
 
         webTestClient.get()
                 .uri("/api/v1/admin/convert/jobs?deadLettered=false")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isOk()
                 .expectBody()
@@ -85,6 +91,7 @@ void deleteJobReturnsNoContent() {
 
         webTestClient.delete()
                 .uri("/api/v1/admin/convert/jobs/" + jobId)
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isNoContent();
     }
@@ -96,6 +103,7 @@ void retryDeadLetteredReturnsAcceptedWhenAccepted() {
 
         webTestClient.post()
                 .uri("/api/v1/admin/convert/jobs/" + jobId + "/retry")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isAccepted();
     }
@@ -107,6 +115,7 @@ void retryDeadLetteredReturnsNotFoundWhenNotFound() {
 
         webTestClient.post()
                 .uri("/api/v1/admin/convert/jobs/" + jobId + "/retry")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isNotFound();
     }
@@ -118,6 +127,7 @@ void retryDeadLetteredReturnsConflictWhenNotEligible() {
 
         webTestClient.post()
                 .uri("/api/v1/admin/convert/jobs/" + jobId + "/retry")
+                .header("X-Dummy", "dummy")
                 .exchange()
                 .expectStatus().isEqualTo(409); // isConflict() isn't always available depending on spring-test version, so using isEqualTo(409) is safer
     }