From ea1deec79c1efc16171451e72e2817ce94c95cfb Mon Sep 17 00:00:00 2001
From: pasta <pasta@dashboost.org>
Date: Thu, 13 Aug 2026 00:10:59 -0500
Subject: [PATCH] fix(coinjoin): snapshot collaterals before random fee
 charging

---
 src/coinjoin/server.cpp | 10 +++++++++-
 src/coinjoin/server.h   |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/coinjoin/server.cpp b/src/coinjoin/server.cpp
index 6d9a3ba16578..f4fd8254d89d 100644
--- a/src/coinjoin/server.cpp
+++ b/src/coinjoin/server.cpp
@@ -490,7 +490,15 @@ void CCoinJoinServer::ChargeFees() const
 */
 void CCoinJoinServer::ChargeRandomFees() const
 {
-    for (const auto& txCollateral : vecSessionCollaterals) {
+    AssertLockNotHeld(cs_coinjoin);
+
+    std::vector<CTransactionRef> session_collaterals;
+    {
+        LOCK(cs_coinjoin);
+        session_collaterals = vecSessionCollaterals;
+    }
+
+    for (const auto& txCollateral : session_collaterals) {
         if (GetRand<int>(/*nMax=*/100) > 10) return;
         LogPrint(BCLog::COINJOIN, /* Continued */
                  "CCoinJoinServer::ChargeRandomFees -- charging random fees, txCollateral=%s", txCollateral->ToString());
diff --git a/src/coinjoin/server.h b/src/coinjoin/server.h
index 0c11576118fd..49cb7a3002d7 100644
--- a/src/coinjoin/server.h
+++ b/src/coinjoin/server.h
@@ -60,7 +60,7 @@ class CCoinJoinServer : public CCoinJoinBaseSession, public NetHandler
     /// Charge fees to bad actors (Charge clients a fee if they're abusive)
     void ChargeFees() const EXCLUSIVE_LOCKS_REQUIRED(!cs_coinjoin);
     /// Rarely charge fees to pay miners
-    void ChargeRandomFees() const;
+    void ChargeRandomFees() const EXCLUSIVE_LOCKS_REQUIRED(!cs_coinjoin);
     /// Consume collateral in cases when peer misbehaved
     void ConsumeCollateral(const CTransactionRef& txref) const;