<p>What malleability means is that you can create a transaction that is identical in its meaning (same inputs, same outputs) but with a different TXID. That is problematic for 2nd layer protocols where transactions build onto each other but aren't necessarily published to chain.</p>

<p>But a "malleated" transaction is still a double spend. And it appears newer versions  of bitcoin-core that support RBF won't accept double spends into their mempool.</p>

<p>See code snippet here: <a href="https://bitcoin.stackexchange.com/questions/58188/validation-error-error-26-258-txn-mempool-conflict">Validation Error: Error #-26: 258: txn-mempool-conflict</a></p>

CC BY-SA 4.0
2020-01-16T16:06:42.097Z
Thanks @guggero, Can I disable RBF in my node? I don't find any option
monkeyUser
CC BY-SA 4.0
2020-01-16T16:32:17.380Z
RBF (as specified in BIP125) only applies when you signature replacement. The problem is here that you don't do that, and as a result the replacement is not accepted.
Pieter Wuille
CC BY-SA 4.0
2020-01-16T16:46:32.727Z
This is unrelated to RBF. Double spends have never been accepted.
Ava Chow
CC BY-SA 4.0
2020-01-16T15:47:35.327Z
2020-01-16T15:47:35.327Z
guggero
<p>I want to replicate transaction malleability to study it.</p>

<p>I have two transactions data signed in testnet.
One it's the original,</p>

<pre><code>0200000001abb6c7df544b53eec11612ab9d82ef0fe0a3aa2ff33f41bbf5f149986d80af47000000006a47304402207a325de81b063d3e28023a63c37c554e7eb136d94612334bbd6715a05abb684e02203a87c85819815bb12d4386fa76aa6b990c65158b61ccb05a14a249e14095663b012103bf7b2ddadda97523405400ae95be2cb153768cce8b1bed55d1c8aca4bb2ee16dffffffff02e8030000000000001976a914fd1002f92de062322225735e24b85590a3ef7af288ac29e31100000000001976a9146162f487e0b293054f1fb8025769f1e1f14d379b88ac00000000
</code></pre>

<p>The second one is the transaction "malleated".</p>

<pre><code>0200000001abb6c7df544b53eec11612ab9d82ef0fe0a3aa2ff33f41bbf5f149986d80af47000000006c527547304402207a325de81b063d3e28023a63c37c554e7eb136d94612334bbd6715a05abb684e02203a87c85819815bb12d4386fa76aa6b990c65158b61ccb05a14a249e14095663b012103bf7b2ddadda97523405400ae95be2cb153768cce8b1bed55d1c8aca4bb2ee16dffffffff02e8030000000000001976a914fd1002f92de062322225735e24b85590a3ef7af288ac29e31100000000001976a9146162f487e0b293054f1fb8025769f1e1f14d379b88ac00000000
</code></pre>

<p>Before send the first one and after send the malleated transaction.</p>

<p>I receive txn-mempool-conflict (code 18)</p>

<p>I can't replicate the transaction malleability if the original is already in the mempool?  </p>

<p>I'm using bitcoin-core 0.19.0.1</p>

<transactions><mempool><transaction-malleability>
Transaction malleability in Testnet
monkeyUser
# Transaction malleability in Testnet

(Asked by: username_0 on 2020-01-16)

I want to replicate transaction malleability to study it.

I have two transactions data signed in testnet.
One it's the original,

```
0200000001abb6c7df544b53eec11612ab9d82ef0fe0a3aa2ff33f41bbf5f149986d80af47000000006a47304402207a325de81b063d3e28023a63c37c554e7eb136d94612334bbd6715a05abb684e02203a87c85819815bb12d4386fa76aa6b990c65158b61ccb05a14a249e14095663b012103bf7b2ddadda97523405400ae95be2cb153768cce8b1bed55d1c8aca4bb2ee16dffffffff02e8030000000000001976a914fd1002f92de062322225735e24b85590a3ef7af288ac29e31100000000001976a9146162f487e0b293054f1fb8025769f1e1f14d379b88ac00000000

```

The second one is the transaction "malleated".

```
0200000001abb6c7df544b53eec11612ab9d82ef0fe0a3aa2ff33f41bbf5f149986d80af47000000006c527547304402207a325de81b063d3e28023a63c37c554e7eb136d94612334bbd6715a05abb684e02203a87c85819815bb12d4386fa76aa6b990c65158b61ccb05a14a249e14095663b012103bf7b2ddadda97523405400ae95be2cb153768cce8b1bed55d1c8aca4bb2ee16dffffffff02e8030000000000001976a914fd1002f92de062322225735e24b85590a3ef7af288ac29e31100000000001976a9146162f487e0b293054f1fb8025769f1e1f14d379b88ac00000000

```

Before send the first one and after send the malleated transaction.

I receive txn-mempool-conflict (code 18)

I can't replicate the transaction malleability if the original is already in the mempool?

I'm using bitcoin-core 0.19.0.1

**Tags:** transactions, mempool, transaction-malleability


---

## 1 answers

### Answer by username_1 on 2020-01-16. Score: 2

What malleability means is that you can create a transaction that is identical in its meaning (same inputs, same outputs) but with a different TXID. That is problematic for 2nd layer protocols where transactions build onto each other but aren't necessarily published to chain.

But a "malleated" transaction is still a double spend. And it appears newer versions of bitcoin-core that support RBF won't accept double spends into their mempool.

See code snippet here: [Validation Error: Error #-26: 258: txn-mempool-conflict](https://bitcoin.stackexchange.com/questions/58188/validation-error-error-26-258-txn-mempool-conflict)

> **Comments:**
> **username_0**: Thanks @username_1, Can I disable RBF in my node? I don't find any option  
> **username_2**: RBF (as specified in BIP125) only applies when you signature replacement. The problem is here that you don't do that, and as a result the replacement is not accepted.  
> **username_3**: This is unrelated to RBF. Double spends have never been accepted.  

---

