diff --git a/crypto/cmp/cmp_msg.c b/crypto/cmp/cmp_msg.c
index 4ba7b81087691..9628f0500ad56 100644
--- a/crypto/cmp/cmp_msg.c
+++ b/crypto/cmp/cmp_msg.c
@@ -145,34 +145,6 @@ static int add1_extension(X509_EXTENSIONS **pexts, int nid, int crit, void *ex)
     return res;
 }
 
-/* Add extension list to the referenced extension stack, which may be NULL */
-static int add_extensions(STACK_OF(X509_EXTENSION) **target,
-                          const STACK_OF(X509_EXTENSION) *exts)
-{
-    int i;
-
-    if (target == NULL)
-        return 0;
-
-    for (i = 0; i < sk_X509_EXTENSION_num(exts); i++) {
-        X509_EXTENSION *ext = sk_X509_EXTENSION_value(exts, i);
-        ASN1_OBJECT *obj = X509_EXTENSION_get_object(ext);
-        int idx = X509v3_get_ext_by_OBJ(*target, obj, -1);
-
-        /* Does extension exist in target? */
-        if (idx != -1) {
-            /* Delete all extensions of same type */
-            do {
-                X509_EXTENSION_free(sk_X509_EXTENSION_delete(*target, idx));
-                idx = X509v3_get_ext_by_OBJ(*target, obj, -1);
-            } while (idx != -1);
-        }
-        if (!X509v3_add_ext(target, ext, -1))
-            return 0;
-    }
-    return 1;
-}
-
 /* Add a CRL revocation reason code to extension stack, which may be NULL */
 static int add_crl_reason_extension(X509_EXTENSIONS **pexts, int reason_code)
 {
@@ -359,7 +331,7 @@ OSSL_CRMF_MSG *OSSL_CMP_CTX_setup_CRM(OSSL_CMP_CTX *ctx, int for_KUR, int rid)
             && !add1_extension(&exts, NID_subject_alt_name, crit, default_sans))
         goto err;
     if (ctx->reqExtensions != NULL /* augment/override existing ones */
-            && !add_extensions(&exts, ctx->reqExtensions))
+            && X509v3_add_extensions(&exts, ctx->reqExtensions) == NULL)
         goto err;
     if (sk_GENERAL_NAME_num(ctx->subjectAltNames) > 0
             && !add1_extension(&exts, NID_subject_alt_name,
diff --git a/crypto/x509/x509_v3.c b/crypto/x509/x509_v3.c
index 1bb0a4b037bff..034b119a2b588 100644
--- a/crypto/x509/x509_v3.c
+++ b/crypto/x509/x509_v3.c
@@ -142,6 +142,36 @@ STACK_OF(X509_EXTENSION) *X509v3_add_ext(STACK_OF(X509_EXTENSION) **x,
     return NULL;
 }
 
+STACK_OF(X509_EXTENSION)
+     *X509v3_add_extensions(STACK_OF(X509_EXTENSION) **target,
+                            const STACK_OF(X509_EXTENSION) *exts)
+{
+    int i;
+
+    if (target == NULL) {
+        ERR_raise(ERR_LIB_X509, ERR_R_PASSED_NULL_PARAMETER);
+        return NULL;
+    }
+
+    for (i = 0; i < sk_X509_EXTENSION_num(exts); i++) {
+        X509_EXTENSION *ext = sk_X509_EXTENSION_value(exts, i);
+        ASN1_OBJECT *obj = X509_EXTENSION_get_object(ext);
+        int idx = X509v3_get_ext_by_OBJ(*target, obj, -1);
+
+        /* Does extension exist in target? */
+        if (idx != -1) {
+            /* Delete all extensions of same type */
+            do {
+                X509_EXTENSION_free(sk_X509_EXTENSION_delete(*target, idx));
+                idx = X509v3_get_ext_by_OBJ(*target, obj, -1);
+            } while (idx != -1);
+        }
+        if (!X509v3_add_ext(target, ext, -1))
+            return NULL;
+    }
+    return *target;
+}
+
 X509_EXTENSION *X509_EXTENSION_create_by_NID(X509_EXTENSION **ex, int nid,
                                              int crit,
                                              ASN1_OCTET_STRING *data)
diff --git a/doc/man3/X509v3_get_ext_by_NID.pod b/doc/man3/X509v3_get_ext_by_NID.pod
index 4010a71c4371a..0974c8641615f 100644
--- a/doc/man3/X509v3_get_ext_by_NID.pod
+++ b/doc/man3/X509v3_get_ext_by_NID.pod
@@ -4,7 +4,7 @@
 
 X509v3_get_ext_count, X509v3_get_ext, X509v3_get_ext_by_NID,
 X509v3_get_ext_by_OBJ, X509v3_get_ext_by_critical, X509v3_delete_ext,
-X509v3_add_ext, X509_get_ext_count, X509_get_ext,
+X509v3_add_ext, X509v3_add_extensions, X509_get_ext_count, X509_get_ext,
 X509_get_ext_by_NID, X509_get_ext_by_OBJ, X509_get_ext_by_critical,
 X509_delete_ext, X509_add_ext, X509_CRL_get_ext_count, X509_CRL_get_ext,
 X509_CRL_get_ext_by_NID, X509_CRL_get_ext_by_OBJ, X509_CRL_get_ext_by_critical,
@@ -29,6 +29,9 @@ X509_REVOKED_add_ext - extension stack utility functions
  X509_EXTENSION *X509v3_delete_ext(STACK_OF(X509_EXTENSION) *x, int loc);
  STACK_OF(X509_EXTENSION) *X509v3_add_ext(STACK_OF(X509_EXTENSION) **x,
                                           X509_EXTENSION *ex, int loc);
+ STACK_OF(X509_EXTENSION)
+      *X509v3_add_extensions(STACK_OF(X509_EXTENSION) **target,
+                             const STACK_OF(X509_EXTENSION) *exts);
 
  int X509_get_ext_count(const X509 *x);
  X509_EXTENSION *X509_get_ext(const X509 *x, int loc);
@@ -79,10 +82,16 @@ X509v3_delete_ext() deletes the extension with index I<loc> from I<x>.
 The deleted extension is returned and must be freed by the caller.
 If I<loc> is an invalid index value, NULL is returned.
 
-X509v3_add_ext() adds extension I<ex> to STACK I<*x> at position I<loc>. If
-I<loc> is -1, the new extension is added to the end. If I<*x> is NULL,
-a new STACK will be allocated. The passed extension I<ex> is duplicated
-internally so it must be freed after use.
+X509v3_add_ext() inserts extension I<ex> to STACK I<*x> at position I<loc>.
+If I<loc> is -1, the new extension is added to the end.
+A new STACK is allocated if I<*x> is NULL.
+The passed extension I<ex> is duplicated so it must be freed after use.
+
+X509v3_add_extensions() adds the list of extensions I<exts> to STACK I<*target>.
+The STACK I<*target> is returned unchanged if I<exts> is NULL or an empty list.
+Otherwise a new stack is allocated if I<*target> is NULL.
+An extension to be added
+that has the same OID as a pre-existing one replaces this earlier one.
 
 X509_get_ext_count(), X509_get_ext(), X509_get_ext_by_NID(),
 X509_get_ext_by_OBJ(), X509_get_ext_by_critical(), X509_delete_ext()
@@ -132,7 +141,8 @@ the extension index or -1 if an error occurs.
 X509v3_get_ext_by_NID() returns the extension index or negative values if an
 error occurs.
 
-X509v3_add_ext() returns a STACK of extensions or NULL on error.
+X509v3_add_ext() and X509v3_add_extensions()
+return a STACK of extensions or NULL on error.
 
 X509_add_ext() returns 1 on success and 0 on error.
 
@@ -140,6 +150,10 @@ X509_add_ext() returns 1 on success and 0 on error.
 
 L<X509V3_get_d2i(3)>
 
+=head1 HISTORY
+
+X509v3_add_extensions() was added in OpenSSL 3.4.
+
 =head1 COPYRIGHT
 
 Copyright 2015-2022 The OpenSSL Project Authors. All Rights Reserved.
diff --git a/include/openssl/x509.h.in b/include/openssl/x509.h.in
index 838dc8cb28ec6..6f13feee09e96 100644
--- a/include/openssl/x509.h.in
+++ b/include/openssl/x509.h.in
@@ -899,6 +899,9 @@ X509_EXTENSION *X509v3_get_ext(const STACK_OF(X509_EXTENSION) *x, int loc);
 X509_EXTENSION *X509v3_delete_ext(STACK_OF(X509_EXTENSION) *x, int loc);
 STACK_OF(X509_EXTENSION) *X509v3_add_ext(STACK_OF(X509_EXTENSION) **x,
                                          X509_EXTENSION *ex, int loc);
+STACK_OF(X509_EXTENSION)
+    *X509v3_add_extensions(STACK_OF(X509_EXTENSION) **target,
+                           const STACK_OF(X509_EXTENSION) *exts);
 
 int X509_get_ext_count(const X509 *x);
 int X509_get_ext_by_NID(const X509 *x, int nid, int lastpos);
diff --git a/util/libcrypto.num b/util/libcrypto.num
index e0474a0021dd9..f6096823999c3 100644
--- a/util/libcrypto.num
+++ b/util/libcrypto.num
@@ -5629,6 +5629,7 @@ X509_ACERT_verify                       ?	3_4_0	EXIST::FUNCTION:
 X509_ACERT_get_ext_d2i                  ?	3_4_0	EXIST::FUNCTION:
 X509_ACERT_add1_ext_i2d                 ?	3_4_0	EXIST::FUNCTION:
 X509_ACERT_get0_extensions              ?	3_4_0	EXIST::FUNCTION:
+X509v3_add_extensions                   ?	3_4_0	EXIST::FUNCTION:
 OSSL_IETF_ATTR_SYNTAX_VALUE_it          ?	3_4_0	EXIST::FUNCTION:
 OSSL_IETF_ATTR_SYNTAX_VALUE_free        ?	3_4_0	EXIST::FUNCTION:
 OSSL_IETF_ATTR_SYNTAX_VALUE_new         ?	3_4_0	EXIST::FUNCTION: