diff --git a/Cargo.lock b/Cargo.lock
index 1d3dc3070..fc7b49de0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8739,6 +8739,7 @@ name = "warp_utils"
 version = "0.1.0"
 dependencies = [
  "beacon_chain",
+ "bytes",
  "eth2",
  "headers",
  "lazy_static",
@@ -8746,6 +8747,7 @@ dependencies = [
  "safe_arith",
  "serde",
  "serde_array_query",
+ "serde_json",
  "state_processing",
  "tokio",
  "types",
diff --git a/beacon_node/http_api/src/lib.rs b/beacon_node/http_api/src/lib.rs
index 91f9047a6..1a8f15225 100644
--- a/beacon_node/http_api/src/lib.rs
+++ b/beacon_node/http_api/src/lib.rs
@@ -682,7 +682,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("validator_balances"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .then(
             |state_id: StateId,
              task_spawner: TaskSpawner<T::EthSpec>,
@@ -726,7 +726,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("validators"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .then(
             |state_id: StateId,
              task_spawner: TaskSpawner<T::EthSpec>,
@@ -1257,7 +1257,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("beacon"))
         .and(warp::path("blocks"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(network_tx_filter.clone())
@@ -1327,7 +1327,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("blocks"))
         .and(warp::query::<api_types::BroadcastValidationQuery>())
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(network_tx_filter.clone())
@@ -1404,7 +1404,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("beacon"))
         .and(warp::path("blinded_blocks"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(network_tx_filter.clone())
@@ -1472,7 +1472,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("blinded_blocks"))
         .and(warp::query::<api_types::BroadcastValidationQuery>())
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(network_tx_filter.clone())
@@ -1754,7 +1754,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("attestations"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .and(log_filter.clone())
         .then(
@@ -1930,7 +1930,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("attester_slashings"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
@@ -1988,7 +1988,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("proposer_slashings"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
@@ -2046,7 +2046,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("voluntary_exits"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
@@ -2102,7 +2102,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("sync_committees"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .and(log_filter.clone())
         .then(
@@ -2139,7 +2139,7 @@ pub fn serve<T: BeaconChainTypes>(
         .clone()
         .and(warp::path("bls_to_execution_changes"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .and(log_filter.clone())
         .then(
@@ -2533,7 +2533,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("attestations"))
         .and(warp::path::param::<Epoch>())
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
              chain: Arc<BeaconChain<T>>,
@@ -2583,7 +2583,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("sync_committee"))
         .and(block_id_or_err)
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(log_filter.clone())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
@@ -3326,7 +3326,7 @@ pub fn serve<T: BeaconChainTypes>(
         }))
         .and(warp::path::end())
         .and(not_while_syncing_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -3352,7 +3352,7 @@ pub fn serve<T: BeaconChainTypes>(
         }))
         .and(warp::path::end())
         .and(not_while_syncing_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -3406,7 +3406,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(not_while_syncing_filter.clone())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter.clone())
         .and(log_filter.clone())
         .then(
@@ -3519,7 +3519,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(not_while_syncing_filter.clone())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(network_tx_filter)
         .and(log_filter.clone())
         .then(
@@ -3545,7 +3545,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("validator"))
         .and(warp::path("beacon_committee_subscriptions"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(validator_subscription_tx_filter.clone())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
@@ -3601,7 +3601,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(log_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
              chain: Arc<BeaconChain<T>>,
@@ -3652,7 +3652,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .and(log_filter.clone())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .then(
             |task_spawner: TaskSpawner<T::EthSpec>,
              chain: Arc<BeaconChain<T>>,
@@ -3826,7 +3826,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("validator"))
         .and(warp::path("sync_committee_subscriptions"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(validator_subscription_tx_filter)
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
@@ -3872,7 +3872,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("liveness"))
         .and(warp::path::param::<Epoch>())
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -3913,7 +3913,7 @@ pub fn serve<T: BeaconChainTypes>(
     let post_lighthouse_liveness = warp::path("lighthouse")
         .and(warp::path("liveness"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -4016,7 +4016,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("ui"))
         .and(warp::path("validator_metrics"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -4035,7 +4035,7 @@ pub fn serve<T: BeaconChainTypes>(
         .and(warp::path("ui"))
         .and(warp::path("validator_info"))
         .and(warp::path::end())
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
         .then(
@@ -4338,7 +4338,7 @@ pub fn serve<T: BeaconChainTypes>(
     let post_lighthouse_block_rewards = warp::path("lighthouse")
         .and(warp::path("analysis"))
         .and(warp::path("block_rewards"))
-        .and(warp::body::json())
+        .and(warp_utils::json::json())
         .and(warp::path::end())
         .and(task_spawner_filter.clone())
         .and(chain_filter.clone())
diff --git a/common/eth2/src/lib.rs b/common/eth2/src/lib.rs
index 16801be8e..6687788d5 100644
--- a/common/eth2/src/lib.rs
+++ b/common/eth2/src/lib.rs
@@ -373,10 +373,30 @@ impl BeaconNodeHttpClient {
         if let Some(timeout) = timeout {
             builder = builder.timeout(timeout);
         }
+
         let response = builder.json(body).send().await?;
         ok_or_error(response).await
     }
 
+    /// Generic POST function supporting arbitrary responses and timeouts.
+    /// Does not include Content-Type application/json in the request header.
+    async fn post_generic_json_without_content_type_header<T: Serialize, U: IntoUrl>(
+        &self,
+        url: U,
+        body: &T,
+        timeout: Option<Duration>,
+    ) -> Result<Response, Error> {
+        let mut builder = self.client.post(url);
+        if let Some(timeout) = timeout {
+            builder = builder.timeout(timeout);
+        }
+
+        let serialized_body = serde_json::to_vec(body).map_err(Error::InvalidJson)?;
+
+        let response = builder.body(serialized_body).send().await?;
+        ok_or_error(response).await
+    }
+
     /// Generic POST function supporting arbitrary responses and timeouts.
     async fn post_generic_with_consensus_version<T: Serialize, U: IntoUrl>(
         &self,
@@ -1250,7 +1270,8 @@ impl BeaconNodeHttpClient {
             .push("pool")
             .push("attester_slashings");
 
-        self.post(path, slashing).await?;
+        self.post_generic_json_without_content_type_header(path, slashing, None)
+            .await?;
 
         Ok(())
     }
diff --git a/common/warp_utils/Cargo.toml b/common/warp_utils/Cargo.toml
index 85c1901ba..0d33de998 100644
--- a/common/warp_utils/Cargo.toml
+++ b/common/warp_utils/Cargo.toml
@@ -14,8 +14,10 @@ beacon_chain = { workspace = true }
 state_processing = { workspace = true }
 safe_arith = { workspace = true }
 serde = { workspace = true }
+serde_json = { workspace = true }
 tokio = { workspace = true }
 headers = "0.3.2"
 lighthouse_metrics = { workspace = true }
 lazy_static = { workspace = true }
 serde_array_query = "0.1.0"
+bytes = { workspace = true }
diff --git a/common/warp_utils/src/json.rs b/common/warp_utils/src/json.rs
new file mode 100644
index 000000000..203a6495a
--- /dev/null
+++ b/common/warp_utils/src/json.rs
@@ -0,0 +1,22 @@
+use bytes::Bytes;
+use serde::de::DeserializeOwned;
+use std::error::Error as StdError;
+use warp::{Filter, Rejection};
+
+use crate::reject;
+
+struct Json;
+
+type BoxError = Box<dyn StdError + Send + Sync>;
+
+impl Json {
+    fn decode<T: DeserializeOwned>(bytes: Bytes) -> Result<T, BoxError> {
+        serde_json::from_slice(&bytes).map_err(Into::into)
+    }
+}
+
+pub fn json<T: DeserializeOwned + Send>() -> impl Filter<Extract = (T,), Error = Rejection> + Copy {
+    warp::body::bytes().and_then(|bytes: Bytes| async move {
+        Json::decode(bytes).map_err(|err| reject::custom_deserialize_error(format!("{:?}", err)))
+    })
+}
diff --git a/common/warp_utils/src/lib.rs b/common/warp_utils/src/lib.rs
index 77d61251f..55ee423fa 100644
--- a/common/warp_utils/src/lib.rs
+++ b/common/warp_utils/src/lib.rs
@@ -2,6 +2,7 @@
 //! Lighthouse project. E.g., the `http_api` and `http_metrics` crates.
 
 pub mod cors;
+pub mod json;
 pub mod metrics;
 pub mod query;
 pub mod reject;
diff --git a/common/warp_utils/src/reject.rs b/common/warp_utils/src/reject.rs
index cf3d11af8..b6bb5ace3 100644
--- a/common/warp_utils/src/reject.rs
+++ b/common/warp_utils/src/reject.rs
@@ -82,6 +82,15 @@ pub fn custom_bad_request(msg: String) -> warp::reject::Rejection {
     warp::reject::custom(CustomBadRequest(msg))
 }
 
+#[derive(Debug)]
+pub struct CustomDeserializeError(pub String);
+
+impl Reject for CustomDeserializeError {}
+
+pub fn custom_deserialize_error(msg: String) -> warp::reject::Rejection {
+    warp::reject::custom(CustomDeserializeError(msg))
+}
+
 #[derive(Debug)]
 pub struct CustomServerError(pub String);
 
@@ -161,6 +170,9 @@ pub async fn handle_rejection(err: warp::Rejection) -> Result<impl warp::Reply,
     if err.is_not_found() {
         code = StatusCode::NOT_FOUND;
         message = "NOT_FOUND".to_string();
+    } else if let Some(e) = err.find::<crate::reject::CustomDeserializeError>() {
+        message = format!("BAD_REQUEST: body deserialize error: {}", e.0);
+        code = StatusCode::BAD_REQUEST;
     } else if let Some(e) = err.find::<warp::filters::body::BodyDeserializeError>() {
         message = format!("BAD_REQUEST: body deserialize error: {}", e);
         code = StatusCode::BAD_REQUEST;