CVE-2021-41217

Null pointer exception when Exit node is not preceded by Enter op

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Attribution

This vulnerability has been reported by members of the Aivul Team from Qihoo 360.

The process of building the control flow graph for a TensorFlow model is vulnerable to a null pointer exception when nodes that should be paired are not:

import tensorflow as tf
  
@tf.function
def func():
  return tf.raw_ops.Exit(data=[False,False])
    
func()

This occurs because the code assumes that the first node in the pairing (e.g., an Enter node) always exists when encountering the second node (e.g., an Exit node):

  ...
} else if (IsExit(curr_node)) {
  // Exit to the parent frame.
  parent = parent_nodes[curr_id];         
  frame_name = cf_info->frame_names[parent->id()];
  ...                

When this is not the case, parent is nullptr so dereferencing it causes a crash.

The application dereferences a null pointer, causing a crash. Typical impact: denial of service via crash.

CVE-2021-41217 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.6.1, 2.5.2, 2.4.4); upgrading removes the vulnerable code path.

Kodem intelligence

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We have patched the issue in GitHub commit 05cbebd3c6bb8f517a158b0155debb8df79017ff.

The fix will be included in TensorFlow 2.7.0. We will also cherrypick this commit on TensorFlow 2.6.1, TensorFlow 2.5.2, and TensorFlow 2.4.4, as these are also affected and still in supported range.

1. What is CVE-2021-41217? CVE-2021-41217 is a medium-severity null pointer dereference vulnerability in tensorflow (pip), affecting versions >= 2.6.0, < 2.6.1. It is fixed in 2.6.1, 2.5.2, 2.4.4. The application dereferences a null pointer, causing a crash.
2. How severe is CVE-2021-41217? CVE-2021-41217 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2021-41217?
   • tensorflow (pip) (versions >= 2.6.0, < 2.6.1)
   • tensorflow-cpu (pip) (versions >= 2.6.0, < 2.6.1)
   • tensorflow-gpu (pip) (versions >= 2.6.0, < 2.6.1)
4. Is there a fix for CVE-2021-41217? Yes. CVE-2021-41217 is fixed in 2.6.1, 2.5.2, 2.4.4. Upgrade to this version or later.
5. Is CVE-2021-41217 exploitable, and should I be worried? Whether CVE-2021-41217 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-41217 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-41217?
   • Upgrade tensorflow to 2.6.1 or later
   • Upgrade tensorflow to 2.5.2 or later
   • Upgrade tensorflow to 2.4.4 or later
   • Upgrade tensorflow-cpu to 2.6.1 or later
   • Upgrade tensorflow-cpu to 2.5.2 or later
   • Upgrade tensorflow-cpu to 2.4.4 or later
   • Upgrade tensorflow-gpu to 2.6.1 or later
   • Upgrade tensorflow-gpu to 2.5.2 or later
   • Upgrade tensorflow-gpu to 2.4.4 or later

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