diff --git a/src/utils/LibBytes.sol b/src/utils/LibBytes.sol
index 8e6fa17703..7541b5b693 100644
--- a/src/utils/LibBytes.sol
+++ b/src/utils/LibBytes.sol
@@ -842,6 +842,32 @@ library LibBytes {
         }
     }
 
+    /// @dev Checks if `x` is in `a`. Assumes `a` has been checked.
+    function checkInCalldata(bytes calldata x, bytes calldata a) internal pure {
+        /// @solidity memory-safe-assembly
+        assembly {
+            if or(
+                or(lt(x.offset, a.offset), gt(add(x.offset, x.length), add(a.length, a.offset))),
+                shr(64, or(x.length, x.offset))
+            ) { revert(0x00, 0x00) }
+        }
+    }
+
+    /// @dev Checks if `x` is in `a`. Assumes `a` has been checked.
+    function checkInCalldata(bytes[] calldata x, bytes calldata a) internal pure {
+        /// @solidity memory-safe-assembly
+        assembly {
+            let e := sub(add(a.length, a.offset), 0x20)
+            if or(lt(x.offset, a.offset), shr(64, x.offset)) { revert(0x00, 0x00) }
+            for { let i := 0 } iszero(eq(x.length, i)) { i := add(i, 1) } {
+                let o := calldataload(add(x.offset, shl(5, i)))
+                let t := add(o, x.offset)
+                let l := calldataload(t)
+                if or(shr(64, or(l, o)), gt(add(t, l), e)) { revert(0x00, 0x00) }
+            }
+        }
+    }
+
     /// @dev Returns empty calldata bytes. For silencing the compiler.
     function emptyCalldata() internal pure returns (bytes calldata result) {
         /// @solidity memory-safe-assembly
diff --git a/src/utils/g/LibBytes.sol b/src/utils/g/LibBytes.sol
index 6b384e0d50..a536ad4d7d 100644
--- a/src/utils/g/LibBytes.sol
+++ b/src/utils/g/LibBytes.sol
@@ -846,6 +846,32 @@ library LibBytes {
         }
     }
 
+    /// @dev Checks if `x` is in `a`. Assumes `a` has been checked.
+    function checkInCalldata(bytes calldata x, bytes calldata a) internal pure {
+        /// @solidity memory-safe-assembly
+        assembly {
+            if or(
+                or(lt(x.offset, a.offset), gt(add(x.offset, x.length), add(a.length, a.offset))),
+                shr(64, or(x.length, x.offset))
+            ) { revert(0x00, 0x00) }
+        }
+    }
+
+    /// @dev Checks if `x` is in `a`. Assumes `a` has been checked.
+    function checkInCalldata(bytes[] calldata x, bytes calldata a) internal pure {
+        /// @solidity memory-safe-assembly
+        assembly {
+            let e := sub(add(a.length, a.offset), 0x20)
+            if or(lt(x.offset, a.offset), shr(64, x.offset)) { revert(0x00, 0x00) }
+            for { let i := 0 } iszero(eq(x.length, i)) { i := add(i, 1) } {
+                let o := calldataload(add(x.offset, shl(5, i)))
+                let t := add(o, x.offset)
+                let l := calldataload(t)
+                if or(shr(64, or(l, o)), gt(add(t, l), e)) { revert(0x00, 0x00) }
+            }
+        }
+    }
+
     /// @dev Returns empty calldata bytes. For silencing the compiler.
     function emptyCalldata() internal pure returns (bytes calldata result) {
         /// @solidity memory-safe-assembly
diff --git a/test/LibBytes.t.sol b/test/LibBytes.t.sol
index 1f92dc974a..a1285f8537 100644
--- a/test/LibBytes.t.sol
+++ b/test/LibBytes.t.sol
@@ -373,4 +373,48 @@ contract LibBytesTest is SoladyTest {
         assertEq(uint160(LibBytes.msbToAddress(x)), msb);
         assertEq(uint160(LibBytes.lsbToAddress(x)), lsb);
     }
+
+    function testCheckInCalldata(bytes memory child) public view {
+        this.checkInCalldata(child, abi.encode(child));
+    }
+
+    function testCheckInCalldata() public pure {
+        LibBytes.checkInCalldata(msg.data, msg.data);
+    }
+
+    function checkInCalldata(bytes calldata expectedChild, bytes calldata encoded) public pure {
+        bytes calldata child;
+        /// @solidity memory-safe-assembly
+        assembly {
+            child.offset := add(0x20, add(encoded.offset, calldataload(encoded.offset)))
+            child.length := calldataload(add(encoded.offset, calldataload(encoded.offset)))
+        }
+        LibBytes.checkInCalldata(child, encoded);
+        LibBytes.checkInCalldata(child, msg.data);
+        LibBytes.checkInCalldata(encoded, msg.data);
+        require(keccak256(expectedChild) == keccak256(child));
+    }
+
+    function testCheckInCalldata(bytes[] memory children) public view {
+        this.checkInCalldata(children, abi.encode(children));
+    }
+
+    function checkInCalldata(bytes[] calldata expectedChildren, bytes calldata encoded)
+        public
+        pure
+    {
+        bytes[] calldata children;
+        /// @solidity memory-safe-assembly
+        assembly {
+            children.offset := add(0x20, add(encoded.offset, calldataload(encoded.offset)))
+            children.length := calldataload(add(encoded.offset, calldataload(encoded.offset)))
+        }
+        LibBytes.checkInCalldata(children, encoded);
+        LibBytes.checkInCalldata(expectedChildren, msg.data);
+        LibBytes.checkInCalldata(children, msg.data);
+        require(expectedChildren.length == children.length);
+        for (uint256 i; i < children.length; ++i) {
+            require(keccak256(expectedChildren[i]) == keccak256(children[i]));
+        }
+    }
 }