diff --git a/components/protocomm/src/crypto/srp6a/esp_srp.c b/components/protocomm/src/crypto/srp6a/esp_srp.c
index c4bbe4cc8c..290ec33021 100644
--- a/components/protocomm/src/crypto/srp6a/esp_srp.c
+++ b/components/protocomm/src/crypto/srp6a/esp_srp.c
@@ -651,6 +651,28 @@ esp_err_t esp_srp_get_session_key(esp_srp_handle_t *hd, char *bytes_A, int len_A
     if (! hd->A) {
         goto error;
     }
+
+    /* RFC 5054 Section 2.5.4: abort if A % N == 0
+     * This prevents an attacker from sending A=0 (or A=k*N) which would
+     * force the shared secret S to zero, yielding a deterministic session
+     * key regardless of the password. */
+    esp_mpi_t *a_mod_n = esp_mpi_new();
+    if (!a_mod_n) {
+        goto error;
+    }
+    if (esp_mpi_a_mod_b(a_mod_n, hd->A, hd->n) != 0) {
+        esp_mpi_free(a_mod_n);
+        ESP_LOGE(TAG, "Failed to compute A mod N");
+        goto error;
+    }
+    int a_mod_n_is_zero = (esp_mpi_cmp_int(a_mod_n, 0) == 0);
+    esp_mpi_free(a_mod_n);
+    if (a_mod_n_is_zero) {
+        ESP_LOGE(TAG, "Rejected client public key: A mod N == 0 (RFC 5054 Section 2.5.4)");
+        ret = ESP_ERR_INVALID_ARG;
+        goto error;
+    }
+
     u = calculate_u(hd, bytes_A, len_A);
     if (! u) {
         goto error;
diff --git a/components/protocomm/src/crypto/srp6a/esp_srp_mpi.c b/components/protocomm/src/crypto/srp6a/esp_srp_mpi.c
index 7798268dea..91a46e8752 100644
--- a/components/protocomm/src/crypto/srp6a/esp_srp_mpi.c
+++ b/components/protocomm/src/crypto/srp6a/esp_srp_mpi.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -129,6 +129,16 @@ int esp_mpi_a_mul_b_mod_c(esp_mpi_t *result, esp_mpi_t *a, esp_mpi_t *b, esp_mpi
     return res;
 }
 
+int esp_mpi_a_mod_b(esp_mpi_t *result, const esp_mpi_t *a, const esp_mpi_t *b)
+{
+    return mbedtls_mpi_mod_mpi(result, a, b);
+}
+
+int esp_mpi_cmp_int(const esp_mpi_t *a, int value)
+{
+    return mbedtls_mpi_cmp_int(a, value);
+}
+
 int esp_mpi_a_add_b_mod_c(esp_mpi_t *result, esp_mpi_t *a, esp_mpi_t *b, esp_mpi_t *c, esp_mpi_ctx_t *ctx)
 {
     (void) ctx;
diff --git a/components/protocomm/src/crypto/srp6a/esp_srp_mpi.h b/components/protocomm/src/crypto/srp6a/esp_srp_mpi.h
index 62095930bb..6b2a96e083 100644
--- a/components/protocomm/src/crypto/srp6a/esp_srp_mpi.h
+++ b/components/protocomm/src/crypto/srp6a/esp_srp_mpi.h
@@ -45,6 +45,10 @@ int esp_mpi_a_mul_b_mod_c(esp_mpi_t *result, esp_mpi_t *a, esp_mpi_t *b, esp_mpi
 
 int esp_mpi_a_add_b_mod_c(esp_mpi_t *result, esp_mpi_t *a, esp_mpi_t *b, esp_mpi_t *c, esp_mpi_ctx_t *ctx);
 
+int esp_mpi_a_mod_b(esp_mpi_t *result, const esp_mpi_t *a, const esp_mpi_t *b);
+
+int esp_mpi_cmp_int(const esp_mpi_t *a, int value);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/components/protocomm/test_apps/main/CMakeLists.txt b/components/protocomm/test_apps/main/CMakeLists.txt
index e12000e008..f5f0e079ae 100644
--- a/components/protocomm/test_apps/main/CMakeLists.txt
+++ b/components/protocomm/test_apps/main/CMakeLists.txt
@@ -1,4 +1,4 @@
 idf_component_register(SRC_DIRS "."
                     PRIV_INCLUDE_DIRS "."
-                    PRIV_REQUIRES cmock mbedtls protocomm protobuf-c test_utils unity
+                    PRIV_REQUIRES cmock mbedtls nvs_flash protocomm protobuf-c test_utils unity
                     WHOLE_ARCHIVE)
diff --git a/components/protocomm/test_apps/main/app_main.c b/components/protocomm/test_apps/main/app_main.c
index 15f7869513..ded6437c19 100644
--- a/components/protocomm/test_apps/main/app_main.c
+++ b/components/protocomm/test_apps/main/app_main.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
@@ -9,6 +9,7 @@
 #include "test_utils.h"
 #include "memory_checks.h"
 #include "esp_newlib.h"
+#include "nvs_flash.h"
 #include "psa/crypto.h"
 // #include "mbedtls/aes.h"
 #if SOC_SHA_SUPPORT_PARALLEL_ENG
@@ -105,5 +106,13 @@ static void test_task(void *pvParameters)
 
 void app_main(void)
 {
+    /* Initialize NVS — required by PSA crypto's ITS backend */
+    esp_err_t ret = nvs_flash_init();
+    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        ESP_ERROR_CHECK(nvs_flash_erase());
+        ret = nvs_flash_init();
+    }
+    ESP_ERROR_CHECK(ret);
+
     xTaskCreatePinnedToCore(test_task, "testTask", CONFIG_UNITY_FREERTOS_STACK_SIZE, NULL, CONFIG_UNITY_FREERTOS_PRIORITY, NULL, CONFIG_UNITY_FREERTOS_CPU);
 }
diff --git a/components/protocomm/test_apps/main/test_srp.c b/components/protocomm/test_apps/main/test_srp.c
index ccd5b46e46..df7237800e 100644
--- a/components/protocomm/test_apps/main/test_srp.c
+++ b/components/protocomm/test_apps/main/test_srp.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
@@ -323,3 +323,90 @@ TEST_CASE("SRP public key randomness test", "[SRP]")
 {
     test_srp_pubkey_randomness();
 }
+
+/* RFC 5054 Section 2.5.4: server MUST abort if A % N == 0
+ * Helper to set up a server-side SRP handle ready for session key derivation */
+static esp_srp_handle_t *setup_srp_server(void)
+{
+    esp_srp_handle_t *handle = esp_srp_init(ESP_NG_3072);
+    TEST_ASSERT_NOT_NULL(handle);
+
+    char *bytes_B = NULL;
+    int len_B = 0;
+    char *bytes_salt = NULL;
+    esp_err_t err = esp_srp_srv_pubkey(handle, username, strlen(username),
+                                       password, strlen(password), 16,
+                                       &bytes_B, &len_B, &bytes_salt);
+    TEST_ASSERT_EQUAL(ESP_OK, err);
+    return handle;
+}
+
+static void test_srp_reject_A_zero(void)
+{
+    esp_srp_handle_t *handle = setup_srp_server();
+
+    /* A = 0: attacker sends all-zero public key */
+    char zero_A[384] = {0};
+    char *bytes_key = NULL;
+    uint16_t len_key = 0;
+    esp_err_t err = esp_srp_get_session_key(handle, zero_A, sizeof(zero_A),
+                                            &bytes_key, &len_key);
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG, err);
+    TEST_ASSERT_NULL(bytes_key);
+
+    esp_srp_free(handle);
+}
+
+/* SRP 3072-bit prime N (same as N_3072 in esp_srp.c) */
+static const char test_N_3072[] = {
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34,
+    0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74,
+    0x02, 0x0B, 0xBE, 0xA6, 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
+    0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, 0xF2, 0x5F, 0x14, 0x37,
+    0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6,
+    0xF4, 0x4C, 0x42, 0xE9, 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
+    0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, 0x7C, 0x4B, 0x1F, 0xE6,
+    0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D, 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05,
+    0x98, 0xDA, 0x48, 0x36, 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F,
+    0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56, 0x20, 0x85, 0x52, 0xBB,
+    0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04,
+    0xF1, 0x74, 0x6C, 0x08, 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B,
+    0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, 0xEC, 0x07, 0xA2, 0x8F,
+    0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9, 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18,
+    0x39, 0x95, 0x49, 0x7C, 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10,
+    0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAA, 0xC4, 0x2D, 0xAD, 0x33, 0x17, 0x0D, 0x04, 0x50, 0x7A, 0x33,
+    0xA8, 0x55, 0x21, 0xAB, 0xDF, 0x1C, 0xBA, 0x64, 0xEC, 0xFB, 0x85, 0x04, 0x58, 0xDB, 0xEF, 0x0A,
+    0x8A, 0xEA, 0x71, 0x57, 0x5D, 0x06, 0x0C, 0x7D, 0xB3, 0x97, 0x0F, 0x85, 0xA6, 0xE1, 0xE4, 0xC7,
+    0xAB, 0xF5, 0xAE, 0x8C, 0xDB, 0x09, 0x33, 0xD7, 0x1E, 0x8C, 0x94, 0xE0, 0x4A, 0x25, 0x61, 0x9D,
+    0xCE, 0xE3, 0xD2, 0x26, 0x1A, 0xD2, 0xEE, 0x6B, 0xF1, 0x2F, 0xFA, 0x06, 0xD9, 0x8A, 0x08, 0x64,
+    0xD8, 0x76, 0x02, 0x73, 0x3E, 0xC8, 0x6A, 0x64, 0x52, 0x1F, 0x2B, 0x18, 0x17, 0x7B, 0x20, 0x0C,
+    0xBB, 0xE1, 0x17, 0x57, 0x7A, 0x61, 0x5D, 0x6C, 0x77, 0x09, 0x88, 0xC0, 0xBA, 0xD9, 0x46, 0xE2,
+    0x08, 0xE2, 0x4F, 0xA0, 0x74, 0xE5, 0xAB, 0x31, 0x43, 0xDB, 0x5B, 0xFC, 0xE0, 0xFD, 0x10, 0x8E,
+    0x4B, 0x82, 0xD1, 0x20, 0xA9, 0x3A, 0xD2, 0xCA, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
+};
+
+static void test_srp_reject_A_equal_N(void)
+{
+    esp_srp_handle_t *handle = setup_srp_server();
+
+    /* A = N: attacker sends the prime itself (N mod N == 0) */
+    char *bytes_key = NULL;
+    uint16_t len_key = 0;
+    esp_err_t err = esp_srp_get_session_key(handle, (char *)test_N_3072,
+                                            sizeof(test_N_3072),
+                                            &bytes_key, &len_key);
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG, err);
+    TEST_ASSERT_NULL(bytes_key);
+
+    esp_srp_free(handle);
+}
+
+TEST_CASE("SRP reject A=0 (RFC 5054 2.5.4)", "[SRP]")
+{
+    test_srp_reject_A_zero();
+}
+
+TEST_CASE("SRP reject A=N (RFC 5054 2.5.4)", "[SRP]")
+{
+    test_srp_reject_A_equal_N();
+}