diff --git a/tools/keytools/keygen.c b/tools/keytools/keygen.c
index e44cff1f..0bf10199 100644
--- a/tools/keytools/keygen.c
+++ b/tools/keytools/keygen.c
@@ -607,6 +607,8 @@ static void keygen_rsa(const char *keyfile, int kbits, uint32_t id_mask,
         exit_code = 4;
         goto cleanup;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key. */
+    setvbuf(fpriv, NULL, _IONBF, 0);
     fwrite(priv_der, privlen, 1, fpriv);
     fclose(fpriv);
     fpriv = NULL;
@@ -687,6 +689,8 @@ static void keygen_ecc(const char *priv_fname, uint16_t ecc_key_size,
         exit_code = 3;
         goto cleanup;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key. */
+    setvbuf(fpriv, NULL, _IONBF, 0);
 
     if (saveAsDer) {
         /* save file as standard ASN.1 / DER */
@@ -794,6 +798,8 @@ static void keygen_ed25519(const char *privkey, uint32_t id_mask)
         exit_code = 3;
         goto cleanup;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key. */
+    setvbuf(fpriv, NULL, _IONBF, 0);
     fwrite(priv, 32, 1, fpriv);
     fwrite(pub, 32, 1, fpriv);
     fclose(fpriv);
@@ -855,6 +861,8 @@ static void keygen_ed448(const char *privkey, uint32_t id_mask)
         exit_code = 3;
         goto cleanup;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key. */
+    setvbuf(fpriv, NULL, _IONBF, 0);
     fwrite(priv, ED448_KEY_SIZE, 1, fpriv);
     fwrite(pub, ED448_PUB_KEY_SIZE, 1, fpriv);
     fclose(fpriv);
@@ -1243,6 +1251,8 @@ static void keygen_ml_dsa(const char *priv_fname, uint32_t id_mask)
         exit_code = 1;
         goto cleanup;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key. */
+    setvbuf(fpriv, NULL, _IONBF, 0);
 
     fwrite(priv, priv_len, 1, fpriv);
     fwrite(pub, pub_len, 1, fpriv);
diff --git a/tools/keytools/sign.c b/tools/keytools/sign.c
index 7f6e8049..43223b68 100644
--- a/tools/keytools/sign.c
+++ b/tools/keytools/sign.c
@@ -709,6 +709,8 @@ static uint8_t *load_key(uint8_t **key_buffer, uint32_t *key_buffer_sz,
         printf("Open key file %s failed\n", key_file);
         goto failure;
     }
+    /* Unbuffered: keep no libc-owned copy of the private key bytes. */
+    setvbuf(f, NULL, _IONBF, 0);
     fseek(f, 0, SEEK_END);
     *key_buffer_sz = ftell(f);
     fseek(f, 0, SEEK_SET);
@@ -717,6 +719,8 @@ static uint8_t *load_key(uint8_t **key_buffer, uint32_t *key_buffer_sz,
         io_sz = (int)fread(*key_buffer, 1, *key_buffer_sz, f);
         if (io_sz != (int)*key_buffer_sz) {
             printf("Key file read error!\n");
+            fclose(f);
+            f = NULL;
             goto failure;
         }
     }
@@ -2480,6 +2484,8 @@ static int make_header_ex(int is_diff, uint8_t *pubkey, uint32_t pubkey_sz,
                     CMD.encrypt_key_file, strerror(errno));
             goto failure;
         }
+        /* Unbuffered: keep no libc-owned copy of the key/IV bytes. */
+        setvbuf(fek, NULL, _IONBF, 0);
         ret = (int)fread(key, 1, keySz, fek);
         if (ret != keySz) {
             fprintf(stderr, "Error reading key from %s\n", CMD.encrypt_key_file);
diff --git a/tools/lms/lms_common.h b/tools/lms/lms_common.h
index f9b12938..0bbe4a2c 100644
--- a/tools/lms/lms_common.h
+++ b/tools/lms/lms_common.h
@@ -52,6 +52,8 @@ static int lms_write_key(const byte * priv, word32 privSz, void * context)
             return WC_LMS_RC_WRITE_FAIL;
         }
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     n_write = fwrite(priv, 1, privSz, file);
 
@@ -74,6 +76,8 @@ static int lms_write_key(const byte * priv, word32 privSz, void * context)
         fprintf(stderr, "error: fopen(%s, \"r+\") failed.\n", filename);
         return WC_LMS_RC_WRITE_FAIL;
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     XMEMSET(buff, 0, n_write);
 
@@ -128,6 +132,8 @@ static int lms_read_key(byte * priv, word32 privSz, void * context)
         fprintf(stderr, "error: fopen(%s, \"rb\") failed\n", filename);
         return WC_LMS_RC_READ_FAIL;
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     n_read = fread(priv, 1, privSz, file);
 
diff --git a/tools/xmss/xmss_common.h b/tools/xmss/xmss_common.h
index 4d152ae6..ed486840 100644
--- a/tools/xmss/xmss_common.h
+++ b/tools/xmss/xmss_common.h
@@ -52,6 +52,8 @@ static enum wc_XmssRc xmss_write_key(const byte * priv, word32 privSz, void * co
             return WC_XMSS_RC_WRITE_FAIL;
         }
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     n_write = fwrite(priv, 1, privSz, file);
 
@@ -74,6 +76,8 @@ static enum wc_XmssRc xmss_write_key(const byte * priv, word32 privSz, void * co
         fprintf(stderr, "error: fopen(%s, \"r+\") failed.\n", filename);
         return WC_XMSS_RC_WRITE_FAIL;
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     buff = malloc(privSz);
     if (buff == NULL) {
@@ -130,6 +134,8 @@ static enum wc_XmssRc xmss_read_key(byte * priv, word32 privSz, void * context)
         fprintf(stderr, "error: fopen(%s, \"rb\") failed\n", filename);
         return WC_XMSS_RC_READ_FAIL;
     }
+    /* Unbuffered: keep no libc-owned copy of the private state. */
+    setvbuf(file, NULL, _IONBF, 0);
 
     n_read = fread(priv, 1, privSz, file);