diff --git a/src/dagre/position/bk.js b/src/dagre/position/bk.js
index d4aabdcef2c788873b799489cf27d48aaa0a2ee6..72beff8b3830f1e3241455400f68843888b60a06 100644
--- a/src/dagre/position/bk.js
+++ b/src/dagre/position/bk.js
@@ -129,6 +129,16 @@ function findOtherInnerSegmentNode(g, v) {
   }
 }
 
+/**
+ * Check if a key is safe to use as an object property to prevent prototype pollution
+ * @param {*} key - The key to check
+ * @returns {boolean} - True if the key is safe, false otherwise
+ */
+function isSafeKey(key) {
+  // Reject prototype pollution vectors
+  return key !== '__proto__' && key !== 'constructor' && key !== 'prototype';
+}
+
 function addConflict(conflicts, v, w) {
   if (v > w) {
     var tmp = v;
@@ -136,6 +146,11 @@ function addConflict(conflicts, v, w) {
     w = tmp;
   }
 
+  // Validate keys to prevent prototype pollution
+  if (!isSafeKey(v) || !isSafeKey(w)) {
+    return;
+  }
+
   var conflictsV = conflicts[v];
   if (!conflictsV) {
     conflicts[v] = conflictsV = {};