From 711971f269ec61fd8f4e108c26c1ddaa7176dd59 Mon Sep 17 00:00:00 2001
From: radik878 <radikpadik76@gmail.com>
Date: Thu, 12 Feb 2026 01:45:50 +0200
Subject: [PATCH] fix: cache slot in check_block_relevancy to prevent TOCTOU
 (#8776)

Co-Authored-By: radik878 <radikpadik76@gmail.com>
---
 beacon_node/beacon_chain/src/block_verification.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/beacon_node/beacon_chain/src/block_verification.rs b/beacon_node/beacon_chain/src/block_verification.rs
index 9bb6757341..e0943d5d93 100644
--- a/beacon_node/beacon_chain/src/block_verification.rs
+++ b/beacon_node/beacon_chain/src/block_verification.rs
@@ -1798,10 +1798,12 @@ pub fn check_block_relevancy<T: BeaconChainTypes>(
 ) -> Result<Hash256, BlockError> {
     let block = signed_block.message();
 
+    let present_slot = chain.slot()?;
+
     // Do not process blocks from the future.
-    if block.slot() > chain.slot()? {
+    if block.slot() > present_slot {
         return Err(BlockError::FutureSlot {
-            present_slot: chain.slot()?,
+            present_slot,
             block_slot: block.slot(),
         });
     }