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fix(cosmossdk): guard nil cursor state in tx history pagination #1277

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fix(cosmossdk): guard nil cursor state in tx history pagination #1277

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9 changes: 9 additions & 0 deletions go/shared/cosmossdk/cursor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,5 +40,14 @@ func (c *Cursor) Decode(b64 string) error {
return errors.Wrapf(err, "failed to unmarshal cursor: %s", bytes)
}

// json.Unmarshal into the existing State map keeps caller-supplied keys and stores a JSON
// null pointer value as a nil *CursorState. Drop those nil entries so a malformed cursor
// (e.g. {"state":{"x":null}}) can't leave a nil pointer to be dereferenced downstream.
for source, state := range c.State {
if state == nil {
delete(c.State, source)
}
}
Comment on lines +43 to +50

@coderabbitai coderabbitai Bot Jun 12, 2026

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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Deleting nil entries can still leave a nil-deref path for expected sources.

At Line 48, deleting c.State[source] removes the initialized entry entirely. In go/shared/cosmossdk/tx.go (context snippet, source-page sync loop), history.Cursor.State[source].Page is dereferenced without an existence check after Decode; a cursor like {"state":{"<expected_source>":null}} can still panic there.

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@go/shared/cosmossdk/cursor.go` around lines 43 - 50, The loop in cursor.go
that deletes nil entries from c.State causes missing keys and can lead to
nil-pointer dereferences later (e.g., history.Cursor.State[source].Page in
tx.go); instead of delete(c.State, source) replace nil values with a non-nil
default (e.g., c.State[source] = &CursorState{} or an equivalent zero-value
CursorState) so the key remains present but safe to dereference; update the loop
that iterates c.State to assign a default CursorState when state == nil.


return nil
}
3 changes: 3 additions & 0 deletions go/shared/cosmossdk/history.go
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,9 @@ func (h *History) filterByCursor(txs []HistoryTx) ([]HistoryTx, error) {
if tx.GetHeight() == h.Cursor.BlockHeight {
found := false
for _, s := range h.Cursor.State {
if s == nil {
continue
}
if tx.GetTxID() == s.TxID {
found = true
break
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