From d5127233e4e39349b29d168fbd15f9105499fa6e Mon Sep 17 00:00:00 2001
From: SashaMalysehko <sashamalysehko@gmail.com>
Date: Fri, 12 Dec 2025 19:09:35 +0200
Subject: [PATCH] fix: missing return after version header check (#16126)

Ensure SubmitAttesterSlashingsV2 returns immediately when the
Eth-Consensus-Version header is missing. Without this early return the
handler calls version.FromString with an empty value and writes a second
JSON error to the response, producing invalid JSON and duplicating error
output. This change aligns the handler with the error-handling pattern
used in other endpoints that validate the version header.
---
 beacon-chain/rpc/eth/beacon/handlers_pool.go  |  1 +
 .../rpc/eth/beacon/handlers_pool_test.go      | 27 +++++++++++++++++++
 .../SashaMalysehko_fix-return-after-check.md  |  3 +++
 3 files changed, 31 insertions(+)
 create mode 100644 changelog/SashaMalysehko_fix-return-after-check.md

diff --git a/beacon-chain/rpc/eth/beacon/handlers_pool.go b/beacon-chain/rpc/eth/beacon/handlers_pool.go
index 09d7eeaa23..b26b298976 100644
--- a/beacon-chain/rpc/eth/beacon/handlers_pool.go
+++ b/beacon-chain/rpc/eth/beacon/handlers_pool.go
@@ -711,6 +711,7 @@ func (s *Server) SubmitAttesterSlashingsV2(w http.ResponseWriter, r *http.Reques
 	versionHeader := r.Header.Get(api.VersionHeader)
 	if versionHeader == "" {
 		httputil.HandleError(w, api.VersionHeader+" header is required", http.StatusBadRequest)
+		return
 	}
 	v, err := version.FromString(versionHeader)
 	if err != nil {
diff --git a/beacon-chain/rpc/eth/beacon/handlers_pool_test.go b/beacon-chain/rpc/eth/beacon/handlers_pool_test.go
index 8fb48692ea..f86734b1b3 100644
--- a/beacon-chain/rpc/eth/beacon/handlers_pool_test.go
+++ b/beacon-chain/rpc/eth/beacon/handlers_pool_test.go
@@ -2112,6 +2112,33 @@ func TestSubmitAttesterSlashingsV2(t *testing.T) {
 		assert.Equal(t, http.StatusBadRequest, e.Code)
 		assert.StringContains(t, "Invalid attester slashing", e.Message)
 	})
+
+	t.Run("missing-version-header", func(t *testing.T) {
+		bs, err := util.NewBeaconStateElectra()
+		require.NoError(t, err)
+
+		broadcaster := &p2pMock.MockBroadcaster{}
+		s := &Server{
+			ChainInfoFetcher: &blockchainmock.ChainService{State: bs},
+			SlashingsPool:    &slashingsmock.PoolMock{},
+			Broadcaster:      broadcaster,
+		}
+
+		var body bytes.Buffer
+		_, err = body.WriteString(invalidAttesterSlashing)
+		require.NoError(t, err)
+		request := httptest.NewRequest(http.MethodPost, "http://example.com/beacon/pool/attester_slashings", &body)
+		// Intentionally do not set api.VersionHeader to verify missing header handling.
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.SubmitAttesterSlashingsV2(writer, request)
+		require.Equal(t, http.StatusBadRequest, writer.Code)
+		e := &httputil.DefaultJsonError{}
+		require.NoError(t, json.Unmarshal(writer.Body.Bytes(), e))
+		assert.Equal(t, http.StatusBadRequest, e.Code)
+		assert.StringContains(t, api.VersionHeader+" header is required", e.Message)
+	})
 }
 
 func TestSubmitProposerSlashing_InvalidSlashing(t *testing.T) {
diff --git a/changelog/SashaMalysehko_fix-return-after-check.md b/changelog/SashaMalysehko_fix-return-after-check.md
new file mode 100644
index 0000000000..65b5a14f66
--- /dev/null
+++ b/changelog/SashaMalysehko_fix-return-after-check.md
@@ -0,0 +1,3 @@
+## Fixed
+
+- Fix missing return after version header check in SubmitAttesterSlashingsV2.