fix(net): bound governance vote signature deserialization

src/Makefile.test.include

@@ -123,6 +123,7 @@ BITCOIN_TESTS =\
   test/governance_inv_tests.cpp \
   test/governance_superblock_tests.cpp \
   test/governance_validators_tests.cpp \
+  test/governance_vote_wire_tests.cpp \
   test/coinjoin_inouts_tests.cpp \
   test/coinjoin_dstxmanager_tests.cpp \
   test/coinjoin_queue_tests.cpp \

src/governance/net_governance.cpp

@@ -193,7 +193,15 @@ void NetGovernance::ProcessMessage(CNode& peer, const std::string& msg_type, CDa
     // A NEW GOVERNANCE OBJECT VOTE HAS ARRIVED
     else if (msg_type == NetMsgType::MNGOVERNANCEOBJECTVOTE) {
         CGovernanceVote vote;
-        vRecv >> vote;
+        // Catch malformed/truncated votes locally so the wire-cap rejection
+        // in CGovernanceVote scores the peer instead of falling through to
+        // the outer log-only handler.
+        try {
+            vRecv >> vote;
+        } catch (const std::ios_base::failure&) {
+            m_peer_manager->PeerMisbehaving(peer.GetId(), 100, "malformed governance vote");
+            return;
+        }
 
         uint256 nHash = vote.GetHash();
 

src/governance/vote.cpp

@@ -9,12 +9,16 @@
 #include <evo/dmn_types.h>
 #include <masternode/sync.h>
 #include <messagesigner.h>
+#include <pubkey.h>
 
 #include <chainparams.h>
 #include <logging.h>
 #include <timedata.h>
 #include <util/string.h>
 
+static_assert(CGovernanceVote::COMPACT_SIG_SIZE == CPubKey::COMPACT_SIGNATURE_SIZE);
+static_assert(CGovernanceVote::BLS_SIG_SIZE == CBLSSignature::SerSize);
+
 std::string CGovernanceVoting::ConvertOutcomeToString(vote_outcome_enum_t nOutcome)
 {
     static const std::map<vote_outcome_enum_t, std::string> mapOutcomeString = {

src/governance/vote.h

@@ -7,6 +7,7 @@
 
 #include <hash.h>
 #include <primitives/transaction.h>
+#include <serialize.h>
 #include <uint256.h>
 #include <util/string.h>
 
@@ -60,6 +61,13 @@ class CGovernanceVote
 
     friend bool operator<(const CGovernanceVote& vote1, const CGovernanceVote& vote2);
 
+public:
+    // Wire-valid signature encodings: compact ECDSA voting key (FUNDING)
+    // or BLS operator key (other signals). Kept in sync via static_assert
+    // against CPubKey::COMPACT_SIGNATURE_SIZE / CBLSSignature::SerSize in vote.cpp.
+    static constexpr size_t COMPACT_SIG_SIZE = 65;
+    static constexpr size_t BLS_SIG_SIZE = 96;
+
 private:
     COutPoint masternodeOutpoint;
     uint256 nParentHash;
@@ -123,7 +131,17 @@ class CGovernanceVote
     {
         READWRITE(obj.masternodeOutpoint, obj.nParentHash, obj.nVoteOutcome, obj.nVoteSignal, obj.nTime);
         if (!(s.GetType() & SER_GETHASH)) {
-            READWRITE(obj.vchSig);
+            // Network reads: cap the signature vector before allocation and require
+            // one of the two legitimate encodings. Other paths (disk, hash, write)
+            // keep the unbounded default.
+            if (ser_action.ForRead() && (s.GetType() & SER_NETWORK)) {
+                READWRITE(LIMITED_VECTOR(obj.vchSig, BLS_SIG_SIZE));
+                if (obj.vchSig.size() != COMPACT_SIG_SIZE && obj.vchSig.size() != BLS_SIG_SIZE) {
+                    throw std::ios_base::failure("bad governance vote signature size");
+                }
+            } else {
+                READWRITE(obj.vchSig);
+            }
         }
         SER_READ(obj, obj.UpdateHash());
     }

src/test/governance_vote_wire_tests.cpp

@@ -0,0 +1,96 @@
+// Copyright (c) 2026 The Dash Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <governance/vote.h>
+#include <primitives/transaction.h>
+#include <serialize.h>
+#include <streams.h>
+#include <uint256.h>
+#include <version.h>
+
+#include <test/util/setup_common.h>
+
+#include <boost/test/unit_test.hpp>
+
+#include <ios>
+#include <limits>
+#include <vector>
+
+BOOST_FIXTURE_TEST_SUITE(governance_vote_wire_tests, BasicTestingSetup)
+
+namespace {
+void WriteVoteHeader(CDataStream& ss)
+{
+    ss << COutPoint{uint256::ONE, 0} << uint256::ONE
+       << int{1} /*outcome*/ << int{1} /*signal*/ << int64_t{1'700'000'000};
+}
+
+CDataStream MakeVoteWire(size_t sig_len)
+{
+    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+    WriteVoteHeader(ss);
+    ss << std::vector<unsigned char>(sig_len, 0xAA);
+    return ss;
+}
+} // namespace
+
+// Reject invalid signature lengths, including a maximal CompactSize prefix.
+BOOST_AUTO_TEST_CASE(rejects_invalid_sizes)
+{
+    for (size_t bad : {size_t{0}, size_t{64}, size_t{66}, size_t{95}, size_t{97}, size_t{128}}) {
+        CDataStream ss = MakeVoteWire(bad);
+        CGovernanceVote vote;
+        BOOST_CHECK_THROW(ss >> vote, std::ios_base::failure);
+    }
+
+    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+    WriteVoteHeader(ss);
+    WriteCompactSize(ss, std::numeric_limits<uint64_t>::max());
+    CGovernanceVote vote;
+    BOOST_CHECK_THROW(ss >> vote, std::ios_base::failure);
+}
+
+// Truncated element bytes must surface as ios_base::failure so the govobjvote
+// handler scores the peer.
+BOOST_AUTO_TEST_CASE(truncated_signature_throws_ios_failure)
+{
+    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+    WriteVoteHeader(ss);
+    ss << uint8_t{CGovernanceVote::BLS_SIG_SIZE};
+    ss.write(MakeByteSpan(std::vector<unsigned char>(10, 0xBB)));
+
+    CGovernanceVote vote;
+    BOOST_CHECK_THROW(ss >> vote, std::ios_base::failure);
+}
+
+// 65-byte ECDSA and 96-byte BLS round-trip cleanly over the network.
+BOOST_AUTO_TEST_CASE(accepts_legitimate_boundary_sizes)
+{
+    for (size_t sig_len : {CGovernanceVote::COMPACT_SIG_SIZE, CGovernanceVote::BLS_SIG_SIZE}) {
+        CDataStream ss = MakeVoteWire(sig_len);
+        const size_t wire_bytes = ss.size();
+
+        CGovernanceVote vote;
+        BOOST_REQUIRE_NO_THROW(ss >> vote);
+        BOOST_CHECK_EQUAL(ss.size(), 0U);
+
+        CDataStream out(SER_NETWORK, PROTOCOL_VERSION);
+        out << vote;
+        BOOST_CHECK_EQUAL(out.size(), wire_bytes);
+    }
+}
+
+// SER_DISK reads stay unbounded — existing on-disk data must load unchanged.
+BOOST_AUTO_TEST_CASE(ser_disk_deserialization_unaffected)
+{
+    CDataStream ss(SER_DISK, PROTOCOL_VERSION);
+    WriteVoteHeader(ss);
+    ss << std::vector<unsigned char>(128, 0xCD);
+
+    CGovernanceVote vote;
+    BOOST_REQUIRE_NO_THROW(ss >> vote);
+    BOOST_CHECK_EQUAL(ss.size(), 0U);
+}
+
+BOOST_AUTO_TEST_SUITE_END()