diff --git a/src/game/packet_parsers_classic.cpp b/src/game/packet_parsers_classic.cpp
index 7077d0ab..046839d0 100644
--- a/src/game/packet_parsers_classic.cpp
+++ b/src/game/packet_parsers_classic.cpp
@@ -4,6 +4,26 @@
 namespace wowee {
 namespace game {
 
+namespace {
+
+bool hasFullPackedGuid(const network::Packet& packet) {
+    if (packet.getReadPos() >= packet.getSize()) {
+        return false;
+    }
+
+    const auto& rawData = packet.getData();
+    const uint8_t mask = rawData[packet.getReadPos()];
+    size_t guidBytes = 1;
+    for (int bit = 0; bit < 8; ++bit) {
+        if ((mask & (1u << bit)) != 0) {
+            ++guidBytes;
+        }
+    }
+    return packet.getSize() - packet.getReadPos() >= guidBytes;
+}
+
+} // namespace
+
 // ============================================================================
 // Classic 1.12.1 movement flag constants
 // Key differences from TBC:
@@ -497,10 +517,10 @@ bool ClassicPacketParsers::parseAttackerStateUpdate(network::Packet& packet, Att
 // ============================================================================
 bool ClassicPacketParsers::parseSpellDamageLog(network::Packet& packet, SpellDamageLogData& data) {
     auto rem = [&]() { return packet.getSize() - packet.getReadPos(); };
-    if (rem() < 2) return false;
+    if (rem() < 2 || !hasFullPackedGuid(packet)) return false;
 
     data.targetGuid   = UpdateObjectParser::readPackedGuid(packet); // PackedGuid in Vanilla
-    if (rem() < 1) return false;
+    if (rem() < 1 || !hasFullPackedGuid(packet)) return false;
     data.attackerGuid = UpdateObjectParser::readPackedGuid(packet); // PackedGuid in Vanilla
 
     // uint32(spellId) + uint32(damage) + uint8(schoolMask) + uint32(absorbed)
@@ -532,10 +552,10 @@ bool ClassicPacketParsers::parseSpellDamageLog(network::Packet& packet, SpellDam
 // ============================================================================
 bool ClassicPacketParsers::parseSpellHealLog(network::Packet& packet, SpellHealLogData& data) {
     auto rem = [&]() { return packet.getSize() - packet.getReadPos(); };
-    if (rem() < 2) return false;
+    if (rem() < 2 || !hasFullPackedGuid(packet)) return false;
 
     data.targetGuid = UpdateObjectParser::readPackedGuid(packet); // PackedGuid in Vanilla
-    if (rem() < 1) return false;
+    if (rem() < 1 || !hasFullPackedGuid(packet)) return false;
     data.casterGuid = UpdateObjectParser::readPackedGuid(packet); // PackedGuid in Vanilla
 
     if (rem() < 13) return false;  // uint32 + uint32 + uint32 + uint8 = 13 bytes