# Disclosure: LND Excessive Failback Exploit

**URL:** <https://delvingbitcoin.org/t/disclosure-lnd-excessive-failback-exploit/1493>\
**Category:** Implementation\
**Tags:** lightning, announcement\
**Created:** [March 4, 2025, 3:58pm UTC](https://delvingbitcoin.org/t/disclosure-lnd-excessive-failback-exploit/1493 "2025-03-04T15:58:58Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![t-bast](https://delvingbitcoin.org/user_avatar/delvingbitcoin.org/t-bast/32/98_2.png) [@t-bast](https://delvingbitcoin.org/u/t-bast)\
**Post date:** [March 24, 2025, 8:53am UTC](https://delvingbitcoin.org/t/disclosure-lnd-excessive-failback-exploit/1493/7 "2025-03-24T08:53:01Z")

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This is hard to follow because it looks like you’re confusing `downstream` and `upstream` in several of your paragraphs…I think I got the gist of it though, but I don’t see how it applies to the change you’re referring to.

The BOLTs change only says that the preimage must be relayed upstream as soon as it’s obtained downstream. At that point we only specify that nodes should correctly extract preimages from downstream and send `update_fulfill_htlc` upstream. This doesn’t change the requirements of whether the node should force-close upstream (if its `update_fulfill_htlc` is not acked) or not.

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_[View the full topic](https://delvingbitcoin.org/t/disclosure-lnd-excessive-failback-exploit/1493)._