Adapted from https://sqlite.org/src/info/5508b56fd24016c1 by Chris Novakovic <chris@chrisn.me.uk>

diff -Naur a/sqlite3.c b/sqlite3.c
--- a/sqlite3.c	2023-11-24 13:34:02.000000000 +0000
+++ b/sqlite3.c	2026-02-04 15:07:10.413293372 +0000
@@ -14912,6 +14912,14 @@
 #define SMALLEST_INT64 (((i64)-1) - LARGEST_INT64)
 
 /*
+** Macro SMXV(n) return the maximum value that can be held in variable n,
+** assuming n is a signed integer type.  UMXV(n) is similar for unsigned
+** integer types.
+*/
+#define SMXV(n) ((((i64)1)<<(sizeof(n)*8-1))-1)
+#define UMXV(n) ((((i64)1)<<(sizeof(n)*8))-1)
+
+/*
 ** Round up a number to the next larger multiple of 8.  This is used
 ** to force 8-byte alignment on 64-bit architectures.
 **
@@ -18682,7 +18690,7 @@
                           ** from source tables rather than from accumulators */
   u8 useSortingIdx;       /* In direct mode, reference the sorting index rather
                           ** than the source table */
-  u16 nSortingColumn;     /* Number of columns in the sorting index */
+  u32 nSortingColumn;     /* Number of columns in the sorting index */
   int sortingIdx;         /* Cursor number of the sorting index */
   int sortingIdxPTab;     /* Cursor number of pseudo-table */
   int iFirstReg;          /* First register in range for aCol[] and aFunc[] */
@@ -18691,8 +18699,8 @@
     Table *pTab;             /* Source table */
     Expr *pCExpr;            /* The original expression */
     int iTable;              /* Cursor number of the source table */
-    i16 iColumn;             /* Column number within the source table */
-    i16 iSorterColumn;       /* Column number in the sorting index */
+    int iColumn;             /* Column number within the source table */
+    int iSorterColumn;       /* Column number in the sorting index */
   } *aCol;
   int nColumn;            /* Number of used entries in aCol[] */
   int nAccumulator;       /* Number of columns that show through to the output.
@@ -114576,7 +114584,9 @@
 ){
   struct AggInfo_col *pCol;
   int k;
+  int mxTerm = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
 
+  assert( mxTerm <= SMXV(i16) );
   assert( pAggInfo->iFirstReg==0 );
   pCol = pAggInfo->aCol;
   for(k=0; k<pAggInfo->nColumn; k++, pCol++){
@@ -114594,6 +114604,10 @@
     assert( pParse->db->mallocFailed );
     return;
   }
+  if( k>mxTerm ){
+    sqlite3ErrorMsg(pParse, "more than %d aggregate terms", mxTerm);
+    k = mxTerm;
+  }
   pCol = &pAggInfo->aCol[k];
   assert( ExprUseYTab(pExpr) );
   pCol->pTab = pExpr->y.pTab;
@@ -114627,6 +114641,7 @@
   if( pExpr->op==TK_COLUMN ){
     pExpr->op = TK_AGG_COLUMN;
   }
+  assert( k <= SMXV(pExpr->iAgg) );
   pExpr->iAgg = (i16)k;
 }
 
@@ -114710,13 +114725,19 @@
         ** function that is already in the pAggInfo structure
         */
         struct AggInfo_func *pItem = pAggInfo->aFunc;
+        int mxTerm = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
+        assert( mxTerm <= SMXV(i16) );
         for(i=0; i<pAggInfo->nFunc; i++, pItem++){
           if( pItem->pFExpr==pExpr ) break;
           if( sqlite3ExprCompare(0, pItem->pFExpr, pExpr, -1)==0 ){
             break;
           }
         }
-        if( i>=pAggInfo->nFunc ){
+        if( i>mxTerm ){
+          sqlite3ErrorMsg(pParse, "more than %d aggregate terms", mxTerm);
+          i = mxTerm;
+          assert( i<pAggInfo->nFunc );
+        }else if( i>=pAggInfo->nFunc ){
           /* pExpr is original.  Make a new entry in pAggInfo->aFunc[]
           */
           u8 enc = ENC(pParse->db);
@@ -114768,6 +114789,7 @@
         */
         assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
         ExprSetVVAProperty(pExpr, EP_NoReduce);
+        assert( i <= SMXV(pExpr->iAgg) );
         pExpr->iAgg = (i16)i;
         pExpr->pAggInfo = pAggInfo;
         return WRC_Prune;