diff -urNp a/snmplib/snmp_api.c b/snmplib/snmp_api.c

--- a/snmplib/snmp_api.c	2020-09-29 14:08:09.821479662 +0200

+++ b/snmplib/snmp_api.c	2020-10-01 10:15:46.607374362 +0200

@@ -2731,7 +2731,7 @@ snmpv3_packet_build(netsnmp_session * se

     /*

      * build a scopedPDU structure into spdu_buf

      */

-    spdu_buf_len = SNMP_MAX_MSG_SIZE;

+    spdu_buf_len = sizeof(spdu_buf);

     DEBUGDUMPSECTION("send", "ScopedPdu");

     cp = snmpv3_scopedPDU_header_build(pdu, spdu_buf, &spdu_buf_len,

                                        &spdu_hdr_e);

@@ -2743,6 +2743,11 @@ snmpv3_packet_build(netsnmp_session * se

      */

     DEBUGPRINTPDUTYPE("send", ((pdu_data) ? *pdu_data : 0x00));

     if (pdu_data) {

+        if (cp + pdu_data_len > spdu_buf + sizeof(spdu_buf)) {

+            snmp_log(LOG_ERR, "%s: PDU too big (%" NETSNMP_PRIz "d > %" NETSNMP_PRIz "d)\n",

+                     __func__, pdu_data_len, sizeof(spdu_buf));

+            return -1;

+        }

         memcpy(cp, pdu_data, pdu_data_len);

         cp += pdu_data_len;

     } else {

@@ -2756,7 +2761,7 @@ snmpv3_packet_build(netsnmp_session * se

      * re-encode the actual ASN.1 length of the scopedPdu

      */

     spdu_len = cp - spdu_hdr_e; /* length of scopedPdu minus ASN.1 headers */

-    spdu_buf_len = SNMP_MAX_MSG_SIZE;

+    spdu_buf_len = sizeof(spdu_buf);

     if (asn_build_sequence(spdu_buf, &spdu_buf_len,

                            (u_char) (ASN_SEQUENCE | ASN_CONSTRUCTOR),

                            spdu_len) == NULL)

@@ -2769,7 +2774,7 @@ snmpv3_packet_build(netsnmp_session * se

      * message - the entire message to transmitted on the wire is returned

      */

     cp = NULL;

-    *out_length = SNMP_MAX_MSG_SIZE;

+    *out_length = sizeof(spdu_buf);

     DEBUGDUMPSECTION("send", "SM msgSecurityParameters");

     sptr = find_sec_mod(pdu->securityModel);

     if (sptr && sptr->encode_forward) {

diff -urNp a/include/net-snmp/library/default_store.h b/include/net-snmp/library/default_store.h

--- a/include/net-snmp/library/default_store.h	2022-03-07 10:50:12.425997555 +0100

+++ b/include/net-snmp/library/default_store.h	2022-03-07 12:51:07.968771327 +0100

@@ -96,7 +96,7 @@ extern          "C" {

 #define NETSNMP_DS_LIB_DNSSEC_WARN_ONLY     41 /* tread DNSSEC errors as warnings */

 #define NETSNMP_DS_LIB_CLIENT_ADDR_USES_PORT 42 /* NETSNMP_DS_LIB_CLIENT_ADDR includes address and also port */

 #define NETSNMP_DS_LIB_MAX_BOOL_ID          48 /* match NETSNMP_DS_MAX_SUBIDS */

-

+#define NETSNMP_DS_LIB_MSG_SEND_MAX        16

     /*

      * library integers 

      */

diff -urNp a/include/net-snmp/library/snmp.h b/include/net-snmp/library/snmp.h

--- a/include/net-snmp/library/snmp.h	2012-10-10 00:28:58.000000000 +0200

+++ b/include/net-snmp/library/snmp.h	2022-03-07 11:27:16.462066135 +0100

@@ -40,6 +40,7 @@ SOFTWARE.

 #define SNMP_MAX_LEN	    1500        /* typical maximum message size */

 #define SNMP_MIN_MAX_LEN    484 /* minimum maximum message size */

+#define SNMP_MAX_PACKET_LEN (0x7fffffff)

     /*

      * SNMP versions 

diff -urNp a/snmplib/snmp_api.c b/snmplib/snmp_api.c

--- a/snmplib/snmp_api.c	2022-03-07 10:50:12.533998393 +0100

+++ b/snmplib/snmp_api.c	2022-03-07 11:18:17.857183065 +0100

@@ -309,6 +309,24 @@ static const char *secLevelName[] = {

 };

 /*

+ * return configured max message size for outgoing packets

+ */

+int

+netsnmp_max_send_msg_size(void)

+{

+    u_int max = netsnmp_ds_get_int(NETSNMP_DS_LIBRARY_ID,

+                                   NETSNMP_DS_LIB_MSG_SEND_MAX);

+    if (0 == max)

+        max = SNMP_MAX_PACKET_LEN;

+    else if (max < SNMP_MIN_MAX_LEN)

+        max = SNMP_MIN_MAX_LEN; /* minimum max size per SNMP specs */

+    else if (max > SNMP_MAX_PACKET_LEN)

+        max = SNMP_MAX_PACKET_LEN;

+

+    return max;

+}

+

+/*

  * Multiple threads may changes these variables.

  * Suggest using the Single API, which does not use Sessions.

  *

@@ -737,7 +755,7 @@ snmp_sess_init(netsnmp_session * session

     session->retries = SNMP_DEFAULT_RETRIES;

     session->version = SNMP_DEFAULT_VERSION;

     session->securityModel = SNMP_DEFAULT_SECMODEL;

-    session->rcvMsgMaxSize = SNMP_MAX_MSG_SIZE;

+    session->rcvMsgMaxSize = netsnmp_max_send_msg_size();

     session->flags |= SNMP_FLAGS_DONT_PROBE;

 }