fix(rpc): validate eth_feeHistory newest_block against chain head (#20969)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

crates/rpc/rpc-eth-api/src/helpers/fee.rs

@@ -13,7 +13,9 @@ use reth_rpc_eth_types::{
     fee_history::calculate_reward_percentiles_for_block, utils::checked_blob_gas_used_ratio,
     EthApiError, FeeHistoryCache, FeeHistoryEntry, GasPriceOracle, RpcInvalidTransactionError,
 };
-use reth_storage_api::{BlockIdReader, BlockReaderIdExt, HeaderProvider, ProviderHeader};
+use reth_storage_api::{
+    BlockIdReader, BlockNumReader, BlockReaderIdExt, HeaderProvider, ProviderHeader,
+};
 use tracing::debug;
 
 /// Fee related functions for the [`EthApiServer`](crate::EthApiServer) trait in the
@@ -92,6 +94,17 @@ pub trait EthFees:
                 newest_block = BlockNumberOrTag::Latest;
             }
 
+            // For explicit block numbers, validate against chain head before resolution
+            if let BlockNumberOrTag::Number(requested) = newest_block {
+                let latest_block =
+                    self.provider().best_block_number().map_err(Self::Error::from_eth_err)?;
+                if requested > latest_block {
+                    return Err(
+                        EthApiError::RequestBeyondHead { requested, head: latest_block }.into()
+                    )
+                }
+            }
+
             let end_block = self
                 .provider()
                 .block_number_for_id(newest_block.into())

crates/rpc/rpc-eth-types/src/error/mod.rs

@@ -92,6 +92,14 @@ pub enum EthApiError {
     /// When an invalid block range is provided
     #[error("invalid block range")]
     InvalidBlockRange,
+    /// Requested block number is beyond the head block
+    #[error("request beyond head block: requested {requested}, head {head}")]
+    RequestBeyondHead {
+        /// The requested block number
+        requested: u64,
+        /// The current head block number
+        head: u64,
+    },
     /// Thrown when the target block for proof computation exceeds the maximum configured window.
     #[error("distance to target block exceeds maximum proof window")]
     ExceedsMaxProofWindow,
@@ -268,6 +276,7 @@ impl From<EthApiError> for jsonrpsee_types::error::ErrorObject<'static> {
             EthApiError::InvalidTransactionSignature |
             EthApiError::EmptyRawTransactionData |
             EthApiError::InvalidBlockRange |
+            EthApiError::RequestBeyondHead { .. } |
             EthApiError::ExceedsMaxProofWindow |
             EthApiError::ConflictingFeeFieldsInRequest |
             EthApiError::Signing(_) |