What the developer wrote
Authored by f321x
qt: fix crash through stale pi resolve
When multiple PIs get resolved consecutively through
repeated editing of the PI field, and the `on_resolve_done`
callback tries to access a PI that has been cleared by
a previous, failed callback an exception is raised.
I was able to reproduce this somehow by adding a sleep to
`PaymentIdentifier._do_resolve()` and entering lightning addresses.
Fixes https://github.com/spesmilo/electrum/issues/10724
What changed, and why it matters
This commit fixes a bug in Electrum's Qt send tab where the app could crash if a user edited the payment recipient field quickly while previous lookups were still finishing. The fix ignores results from outdated lookups instead of letting them trigger an error.
Apply the patch. It is a low-risk defensive fix that prevents UI crashes. No immediate security response is needed beyond normal update cadence.
Security signals we found
Fixes a race condition between asynchronous resolve callbacks and UI state
Prevents exception/crash from stale callback accessing invalid state
Issue reference suggests reproducible crash via timing manipulation
Evidence from the diff
The patch adds a guard in on_resolve_done() in electrum/gui/qt/send_tab.py that checks whether the resolved PaymentIdentifier (pi) still matches the current value of self.payto_e.payment_identifier. If it does not, the callback returns early, preventing a stale resolve result from being processed after the user has already changed or cleared the field. This avoids an exception caused by accessing a cleared or replaced PI.
Changed components
electrum/gui/qt/send_tab.pyPaymentIdentifier resolution flow in Qt send tabInspect captured patch +4 / −0
diff --git a/electrum/gui/qt/send_tab.py b/electrum/gui/qt/send_tab.py
index 6da1c54..91d4e72 100644
--- a/electrum/gui/qt/send_tab.py
+++ b/electrum/gui/qt/send_tab.py
@@ -493,6 +493,10 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
def on_resolve_done(self, pi: 'PaymentIdentifier'):
# TODO: resolve can happen while typing, we don't want message dialogs to pop up
# currently we don't set error for emaillike recipients to avoid just that
+ if pi != self.payto_e.payment_identifier:
+ self.logger.debug(f"stale resolve done")
+ return
+
self.logger.debug('payment identifier resolve done')
self.spinner.setVisible(False)
if pi.error:
Why this scored 24/100
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