CVE-2021-37639 (published 2021-08-12T19:15Z)

TensorFlow is an end-to-end open source platform for machine learning. When restoring tensors via raw APIs, if the tensor name is not provided, TensorFlow can be tricked into dereferencing a null pointer. Alternatively, attackers can read memory outside the bounds of heap allocated data by providing some tensor names but not enough for a successful restoration. The [implementation](https://github.com/tensorflow/tensorflow/blob/47a06f40411a69c99f381495f490536972152ac0/tensorflow/core/kernels/save_restore_tensor.cc#L158-L159) retrieves the tensor list corresponding to the `tensor_name` user controlled input and immediately retrieves the tensor at the restoration index (controlled via `preferred_shard` argument). This occurs without validating that the provided list has enough values. If the list is empty this results in dereferencing a null pointer (undefined behavior). If, however, the list has some elements, if the restoration index is outside the bounds this results in heap OOB read. We have patched the issue in GitHub commit 9e82dce6e6bd1f36a57e08fa85af213e2b2f2622. The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, as these are also affected and still in supported range.

Severity: MEDIUM
CVSS v2 base score: 4.6 (AV:L/AC:L/Au:N/C:P/I:P/A:P)
CVSS v3 base score: 7.8, HIGH (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-125
cwe_name: Out-of-bounds Read
description: The product reads data past the end, or before the beginning, of the intended buffer.
extended_description: 
            
            
             
			 
         
         
cwe_id: CWE-476
cwe_name: NULL Pointer Dereference
description: The product dereferences a pointer that it expects to be valid but is NULL.
extended_description: 
            
            
            
         
         

Fix information:
repo_url: https://github.com/tensorflow/tensorflow
commit_details: repo_url: https://github.com/tensorflow/tensorflow
author: Mihai Maruseac
author_date: 2021-08-02 14:21:41-07:00
msg: Fix NPE in restoring code.

PiperOrigin-RevId: 388303253
Change-Id: Ia8c68568cb854bca538909a182b31a618d68ce55
repository: repo_url: https://github.com/tensorflow/tensorflow
repo_name: tensorflow/tensorflow
description: An Open Source Machine Learning Framework for Everyone
repo_language: C++
owner: tensorflow
file_changes: filename: save_restore_tensor.cc
change_type: ModificationType.MODIFY
diff: @@ -151,11 +151,18 @@ void RestoreTensor(OpKernelContext* context,
         context, size == 1,
         errors::InvalidArgument(
             "Input 0 (file_pattern) must be a string scalar; got a tensor of ",
-            size, "elements"));
+            size, " elements"));
   }
   const string& file_pattern = file_pattern_t.flat<tstring>()(0);
 
   const Tensor& tensor_name_t = context->input(1);
+  {
+    const int64_t size = tensor_name_t.NumElements();
+    OP_REQUIRES(context, size > restore_index,
+                errors::InvalidArgument(
+                    "Input 1 (file_pattern) must be a have at least ",
+                    restore_index + 1, " elements"));
+  }
   const string& tensor_name = tensor_name_t.flat<tstring>()(restore_index);
 
   // If we cannot find a cached reader we will allocate our own.

programming_language: C++