From 31bc25973a612d451f7477f679b9f79640f2f4fb Mon Sep 17 00:00:00 2001
From: tequ <git@tequ.dev>
Date: Mon, 13 Apr 2026 15:55:16 +0900
Subject: [PATCH] fix SponsorshipSet Update FeeAmount Lacks Reserve Floor Check

---
 src/libxrpl/tx/transactors/Sponsor/SponsorshipSet.cpp | 10 ++++++++++
 src/test/app/Sponsor_test.cpp                         | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/libxrpl/tx/transactors/Sponsor/SponsorshipSet.cpp b/src/libxrpl/tx/transactors/Sponsor/SponsorshipSet.cpp
index 376cb6afc6..28f9029721 100644
--- a/src/libxrpl/tx/transactors/Sponsor/SponsorshipSet.cpp
+++ b/src/libxrpl/tx/transactors/Sponsor/SponsorshipSet.cpp
@@ -295,6 +295,16 @@ SponsorshipSet::doApply()
                 (*sponsorObjSle).makeFieldAbsent(sfFeeAmount);
             else
                 (*sponsorObjSle).setFieldAmount(sfFeeAmount, *feeAmount);
+
+            if (auto const ret = checkInsufficientReserve(
+                    ctx_.view(),
+                    ctx_.tx,
+                    sponsorAccSle,
+                    STAmount{(*sponsorAccSle)[sfBalance]}.xrp(),
+                    reserveSponsorAccSle,
+                    0);
+                !isTesSuccess(ret))
+                return tecUNFUNDED;
         }
     }
 
diff --git a/src/test/app/Sponsor_test.cpp b/src/test/app/Sponsor_test.cpp
index cad1892fca..41b5e88b65 100644
--- a/src/test/app/Sponsor_test.cpp
+++ b/src/test/app/Sponsor_test.cpp
@@ -256,6 +256,16 @@ public:
             fee(XRP(1)),
             ter(tecUNFUNDED));
         env.close();
+
+        // Increasing feeAmount to reach insufficient reserve
+        auto const currentFeeAmount =
+            env.le(keylet::sponsor(sponsor.id(), alice.id()))->getFieldAmount(sfFeeAmount).xrp();
+        adjustAccountXRPBalance(env, sponsor, XRP(310));
+        env(sponsor::set_fee(sponsor, 0, currentFeeAmount + XRP(309)),
+            sponsor::sponseeAcc(alice),
+            fee(XRP(1)),
+            ter(tecUNFUNDED));
+        env.close();
     }
 
     void