diff --git a/crates/aaf/src/aaf/store.rs b/crates/aaf/src/aaf/store.rs
index 46ab95dae..69b14fcf2 100644
--- a/crates/aaf/src/aaf/store.rs
+++ b/crates/aaf/src/aaf/store.rs
@@ -377,6 +377,7 @@ const MAX_PATH_BYTES: usize = 64 << 20;
 /// Parse the object tree of an AAF compound file (the root object).
 pub(crate) fn read(bytes: &[u8]) -> Result<Obj, String> {
     let cf = CompoundFile::open(bytes).map_err(|e| e.to_string())?;
+    cf.validate_root_chain().map_err(|e| e.to_string())?;
     let mut paths = Vec::new();
     if let Ok(rp) = cf.read_path("referenced properties")
         && rp.len() >= 7
diff --git a/crates/cfb/src/read.rs b/crates/cfb/src/read.rs
index decd895da..b0eedde3e 100644
--- a/crates/cfb/src/read.rs
+++ b/crates/cfb/src/read.rs
@@ -424,6 +424,19 @@ impl<'a> CompoundFile<'a> {
         self.entries.first().unwrap_or(&EMPTY)
     }
 
+    /// Reject a cycle or invalid link anywhere in the root mini-stream sector chain.
+    /// Opening remains tolerant so other streams can still be salvaged.
+    pub fn validate_root_chain(&self) -> Result<()> {
+        let root = self.root();
+        if root.size > 0 {
+            if root.start == ENDOFCHAIN {
+                return Err(invalid("nonempty root mini stream has no sector chain"));
+            }
+            self.chain_ids(root.start, None)?;
+        }
+        Ok(())
+    }
+
     pub fn entry(&self, id: usize) -> Option<&Entry> {
         self.entries.get(id)
     }
diff --git a/crates/cfb/src/tests/ported.rs b/crates/cfb/src/tests/ported.rs
index f29eb7ea9..7e9a284df 100644
--- a/crates/cfb/src/tests/ported.rs
+++ b/crates/cfb/src/tests/ported.rs
@@ -702,3 +702,14 @@ fn special_values_in_every_field_never_panic() {
         }
     }
 }
+
+#[test]
+fn strict_root_validation_rejects_a_loop_beyond_declared_mini_stream() {
+    let data = pattern(100, 1);
+    let mut file = foreign_file(&[("Small", &data)]);
+    let root = dir_at(&file, 0);
+    let start = u32::from_le_bytes(file[root + 116..root + 120].try_into().unwrap());
+    put_u32(&mut file, 512 + start as usize * 4, start);
+    let cf = CompoundFile::open(&file).unwrap();
+    assert!(cf.validate_root_chain().is_err());
+}