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diff --git a/stateless/test_witness_keys.nim b/stateless/test_witness_keys.nim
index 93e160916..95904c0ac 100644
--- a/stateless/test_witness_keys.nim
+++ b/stateless/test_witness_keys.nim
@@ -1,5 +1,5 @@
 import
-  randutils, random, unittest2, stew/byteutils,
+  randutils, random, unittest2, stew/byteutils, os,
   eth/[common, rlp], eth/trie/[hexary, db, trie_defs, nibbles],
   faststreams/inputs, nimcrypto/sysrand,
   ../stateless/[witness_from_tree, tree_from_witness],
@@ -124,6 +124,14 @@ proc initMultiKeys(keys: openArray[string]): MultikeysRef =
       hash: hexToByteArray[32](x)
     )
 
+proc parseInvalidInput(payload: openArray[byte]): bool =
+  var db = newMemoryDB()
+  try:
+    var tb = initTreeBuilder(payload, db, {wfEIP170})
+    discard tb.buildTree()
+  except ParsingError, ContractCodeError:
+    result = true
+
 proc witnessKeysMain*() =
   suite "random keys block witness roundtrip test":
     randomize()
@@ -223,5 +231,10 @@ proc witnessKeysMain*() =
         mg.group.first == 2
         mg.group.last == 3
 
+    test "parse invalid input":
+      for x in walkDirRec("stateless" / "invalidInput"):
+        let z = readFile(x)
+        check parseInvalidInput(z.toOpenArrayByte(0, z.len-1))
+
 when isMainModule:
   witnessKeysMain()
diff --git a/stateless/tree_from_witness.nim b/stateless/tree_from_witness.nim
index d0ba39070..cc75c2bd5 100644
--- a/stateless/tree_from_witness.nim
+++ b/stateless/tree_from_witness.nim
@@ -218,7 +218,9 @@ proc buildForest*(t: var TreeBuilder): seq[KeccakHash]
     result.add KeccakHash(data: res.data)
 
 proc treeNode(t: var TreeBuilder, depth: int, storageMode = false): NodeKey =
-  assert(depth < 64)
+  if depth >= 64:
+    raise newException(ParsingError, "invalid trie structure")
+
   let nodeType = safeReadEnum(t, TrieNodeType)
   case nodeType
   of BranchNodeType: result = t.branchNode(depth, storageMode)
@@ -235,7 +237,9 @@ proc treeNode(t: var TreeBuilder, depth: int, storageMode = false): NodeKey =
     result = t.forceSmallNodeKeyToHash(result)
 
 proc branchNode(t: var TreeBuilder, depth: int, storageMode: bool): NodeKey =
-  assert(depth < 64)
+  if depth >= 64:
+    raise newException(ParsingError, "invalid trie structure")
+
   let mask = constructBranchMask(t.safeReadByte, t.safeReadByte)
 
   when defined(debugDepth):
@@ -305,9 +309,13 @@ func hexPrefixLeaf(r: var RlpWriter, x: openArray[byte], depth: int) =
   r.append toOpenArray(bytes, 0, nibblesLen div 2)
 
 proc extensionNode(t: var TreeBuilder, depth: int, storageMode: bool): NodeKey =
-  assert(depth < 63)
+  if depth >= 63:
+    raise newException(ParsingError, "invalid trie structure")
+
   let nibblesLen = t.safeReadByte().int
-  assert(nibblesLen < 65)
+  if nibblesLen > 64 or nibblesLen < 1:
+    raise newException(ParsingError, "nibblesLen should between 1..64")
+
   var r = initRlpList(2)
   let pathLen = nibblesLen div 2 + nibblesLen mod 2
   safeReadBytes(t, pathLen):
@@ -321,7 +329,9 @@ proc extensionNode(t: var TreeBuilder, depth: int, storageMode: bool): NodeKey =
     var hash: NodeKey
     toKeccak(hash, t.read(32))
 
-  assert(depth + nibblesLen < 65)
+  if nibblesLen + depth > 64 or nibblesLen + depth < 1:
+    raise newException(ParsingError, "depth should between 1..64")
+
   let nodeType = safeReadEnum(t, TrieNodeType)
   case nodeType
   of BranchNodeType: r.append t.branchNode(depth + nibblesLen, storageMode)
@@ -375,7 +385,8 @@ proc readByteCode(t: var TreeBuilder, acc: var Account) =
     acc.codeHash.data = codeHash.data
 
 proc accountNode(t: var TreeBuilder, depth: int): NodeKey =
-  assert(depth < 65)
+  if depth >= 65:
+    raise newException(ParsingError, "invalid trie structure")
 
   when defined(debugHash):
     let len = t.safeReadU32().int
@@ -443,7 +454,8 @@ proc readStorageSlot(t: var TreeBuilder): Hash256 =
     t.keys[^1].slots.add slot
 
 proc accountStorageLeafNode(t: var TreeBuilder, depth: int): NodeKey =
-  assert(depth < 65)
+  if depth >= 65:
+    raise newException(ParsingError, "invalid trie structure")
 
   when defined(debugHash):
     let len = t.safeReadU32().int