diff --git a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/io/FrameInputBuffer.java b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/io/FrameInputBuffer.java
index 376f26d1a..716f7b74f 100644
--- a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/io/FrameInputBuffer.java
+++ b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/io/FrameInputBuffer.java
@@ -38,6 +38,7 @@
 import org.apache.hc.core5.http2.H2TransportMetrics;
 import org.apache.hc.core5.http2.frame.FrameConsts;
 import org.apache.hc.core5.http2.frame.FrameFlag;
+import org.apache.hc.core5.http2.frame.FrameType;
 import org.apache.hc.core5.http2.frame.RawFrame;
 import org.apache.hc.core5.http2.impl.BasicH2TransportMetrics;
 import org.apache.hc.core5.util.Args;
@@ -112,7 +113,7 @@ public RawFrame read(final InputStream inStream) throws IOException {
         final int frameLen = payloadOff + payloadLen;
         fillBuffer(inStream, frameLen);
 
-        if ((flags & FrameFlag.PADDED.getValue()) > 0) {
+        if ((flags & FrameFlag.PADDED.getValue()) > 0 && isPaddedFrameType(type)) {
             if (payloadLen == 0) {
                 throw new H2ConnectionException(H2Error.PROTOCOL_ERROR, "Inconsistent padding");
             }
@@ -137,4 +138,10 @@ public H2TransportMetrics getMetrics() {
         return metrics;
     }
 
+    private static boolean isPaddedFrameType(final int type) {
+        return FrameType.DATA.same(type)
+                || FrameType.HEADERS.same(type)
+                || FrameType.PUSH_PROMISE.same(type);
+    }
+
 }
diff --git a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/FrameInputBuffer.java b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/FrameInputBuffer.java
index 009f75d3d..b1fb48022 100644
--- a/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/FrameInputBuffer.java
+++ b/httpcore5-h2/src/main/java/org/apache/hc/core5/http2/impl/nio/FrameInputBuffer.java
@@ -36,6 +36,7 @@
 import org.apache.hc.core5.http2.H2TransportMetrics;
 import org.apache.hc.core5.http2.frame.FrameConsts;
 import org.apache.hc.core5.http2.frame.FrameFlag;
+import org.apache.hc.core5.http2.frame.FrameType;
 import org.apache.hc.core5.http2.frame.RawFrame;
 import org.apache.hc.core5.http2.impl.BasicH2TransportMetrics;
 import org.apache.hc.core5.util.Args;
@@ -150,12 +151,12 @@ public RawFrame read(final ByteBuffer src, final ReadableByteChannel channel) th
                     }
                 case PAYLOAD_EXPECTED:
                     if (buffer.remaining() >= payloadLen) {
-                        if ((flags & FrameFlag.PADDED.getValue()) > 0) {
+                        if ((flags & FrameFlag.PADDED.getValue()) > 0 && isPaddedFrameType(type)) {
                             if (payloadLen == 0) {
                                 throw new H2ConnectionException(H2Error.PROTOCOL_ERROR, "Inconsistent padding");
                             }
                             buffer.mark();
-                            final int padding = buffer.get();
+                            final int padding = buffer.get() & 0xff;
                             if (payloadLen < padding + 1) {
                                 throw new H2ConnectionException(H2Error.PROTOCOL_ERROR, "Inconsistent padding");
                             }
@@ -204,6 +205,12 @@ public RawFrame read(final ReadableByteChannel channel) throws IOException {
         return read(null, channel);
     }
 
+    private static boolean isPaddedFrameType(final int type) {
+        return FrameType.DATA.same(type)
+                || FrameType.HEADERS.same(type)
+                || FrameType.PUSH_PROMISE.same(type);
+    }
+
     public void reset() {
         buffer.compact();
         state = State.HEAD_EXPECTED;
diff --git a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/io/TestFrameInOutBuffers.java b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/io/TestFrameInOutBuffers.java
index 617f59982..4af0dc6b1 100644
--- a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/io/TestFrameInOutBuffers.java
+++ b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/io/TestFrameInOutBuffers.java
@@ -34,6 +34,7 @@
 import org.apache.hc.core5.http.ConnectionClosedException;
 import org.apache.hc.core5.http2.H2ConnectionException;
 import org.apache.hc.core5.http2.H2CorruptFrameException;
+import org.apache.hc.core5.http2.H2Error;
 import org.apache.hc.core5.http2.frame.FrameConsts;
 import org.apache.hc.core5.http2.frame.FrameFlag;
 import org.apache.hc.core5.http2.frame.FrameType;
@@ -244,5 +245,36 @@ void testReadFrameExceedingLimit() {
         Assertions.assertThrows(H2ConnectionException.class, () -> inBuffer.read(inputStream));
     }
 
+    @Test
+    void testPaddedBitOnUnknownFrameTypeIgnored() throws Exception {
+        final FrameInputBuffer inBuffer = new FrameInputBuffer(16 * 1024);
+        final ByteArrayInputStream inputStream = new ByteArrayInputStream(
+                new byte[] {
+                        0, 0, 1, 10, 8, 0, 0, 0, 1, 42 // len=1,type=0x0a(flags=0x08),stream=1,payload=42
+                });
+
+        final RawFrame frame = inBuffer.read(inputStream);
+        Assertions.assertNotNull(frame);
+        Assertions.assertEquals(0x0a, frame.getType());
+        Assertions.assertEquals(0x08, frame.getFlags());
+        Assertions.assertEquals(1, frame.getStreamId());
+        Assertions.assertEquals(1, frame.getLength());
+        Assertions.assertNotNull(frame.getPayload());
+        Assertions.assertEquals(1, frame.getPayload().remaining());
+        Assertions.assertEquals(42, frame.getPayload().get() & 0xff);
+    }
+
+    @Test
+    void testPaddedValidationAppliedForDataFrame() {
+        final FrameInputBuffer inBuffer = new FrameInputBuffer(16 * 1024);
+        final ByteArrayInputStream inputStream = new ByteArrayInputStream(
+                new byte[] {
+                        0, 0, 1, 0, 8, 0, 0, 0, 1, 42 // len=1,type=DATA(flags=0x08),stream=1,padLength=42 -> invalid
+                });
+
+        final H2ConnectionException ex = Assertions.assertThrows(H2ConnectionException.class, () -> inBuffer.read(inputStream));
+        Assertions.assertEquals(H2Error.PROTOCOL_ERROR.getCode(), ex.getCode());
+    }
+
 }
 
diff --git a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestFrameInputBuffer.java b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestFrameInputBuffer.java
index 88f07e240..baa29c638 100644
--- a/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestFrameInputBuffer.java
+++ b/httpcore5-h2/src/test/java/org/apache/hc/core5/http2/impl/nio/TestFrameInputBuffer.java
@@ -106,4 +106,44 @@ void streamIdReservedBitMustBeIgnored() throws Exception {
         assertNotNull(rawFrame);
         assertEquals(1, rawFrame.getStreamId());
     }
+
+    @Test
+    void paddedBitOnUnknownFrameTypeMustBeIgnored() throws Exception {
+        final byte[] frame = new byte[]{
+                0x00, 0x00, 0x01, 0x0a, // length=1 + type=0x0a (unknown)
+                0x08,                   // PADDED bit set (undefined for this type)
+                0x00, 0x00, 0x00, 0x01, // streamId = 1
+                0x2a                    // payload byte
+        };
+
+        final FrameInputBuffer inBuf = new FrameInputBuffer(16 * 1024);
+        final ReadableByteChannel ch = Channels.newChannel(new ByteArrayInputStream(frame));
+
+        final RawFrame rawFrame = inBuf.read(ch);
+        assertNotNull(rawFrame);
+        assertEquals(0x0a, rawFrame.getType());
+        assertEquals(0x08, rawFrame.getFlags());
+        assertEquals(1, rawFrame.getStreamId());
+        assertEquals(1, rawFrame.getLength());
+        assertNotNull(rawFrame.getPayload());
+        assertEquals(1, rawFrame.getPayload().remaining());
+        assertEquals(0x2a, rawFrame.getPayload().get() & 0xff);
+    }
+
+    @Test
+    void paddedSemanticsStillApplyToDataFrames() throws Exception {
+        // DATA frame with PADDED flag and payloadLen=1, padding=0x2a -> invalid.
+        // This ensures the padded-validation branch is still entered for valid frame types.
+        final byte[] frame = new byte[]{
+                0x00, 0x00, 0x01, 0x00, // length=1 + type=DATA
+                0x08,                   // PADDED
+                0x00, 0x00, 0x00, 0x01, // streamId = 1
+                0x2a                    // pad length byte (invalid for payloadLen=1)
+        };
+
+        final FrameInputBuffer inBuf = new FrameInputBuffer(16 * 1024);
+        final ReadableByteChannel ch = Channels.newChannel(new ByteArrayInputStream(frame));
+        final H2ConnectionException ex = assertThrows(H2ConnectionException.class, () -> inBuf.read(ch));
+        assertEquals(H2Error.PROTOCOL_ERROR.getCode(), ex.getCode());
+    }
 }