CVE-2021-29521 Explained : Impact and Mitigation

This article discusses a vulnerability in TensorFlow that leads to a segmentation fault due to an incorrect calculation of buffer size.

Understanding CVE-2021-29521

This CVE involves TensorFlow, an open-source platform for machine learning, and highlights the impact, technical details, and mitigation strategies.

What is CVE-2021-29521?

TensorFlow's

SparseCountSparseOutput

encounters a segmentation fault when a negative dense shape is specified, resulting from broken invariants within the standard library. The issue arises from assuming the first element of the dense shape is always positive.

The Impact of CVE-2021-29521

This vulnerability has a low severity score with a CVSS base score of 2.5. It affects certain versions of TensorFlow, potentially leading to service disruption.

Technical Details of CVE-2021-29521

The vulnerability stems from an incorrect calculation of buffer size within TensorFlow, impacting specific product versions.

Vulnerability Description

The segmentation fault in

tf.raw_ops.SparseCountSparseOutput

is caused by assuming a positive first element in the dense shape.

Affected Systems and Versions

Versions prior to 2.3.3 and versions between 2.4.0 to 2.4.2 of TensorFlow are affected by this vulnerability.

Exploitation Mechanism

The vulnerability can be exploited by specifying a negative dense shape, triggering a segmentation fault due to incorrect buffer size calculation.

Mitigation and Prevention

Understanding the issue and applying appropriate patches are crucial to prevent exploitation and maintain system security.

Immediate Steps to Take

Users are advised to update to TensorFlow 2.3.3 or apply patches from TensorFlow 2.4.2 to mitigate the vulnerability.

Long-Term Security Practices

Regularly updating software and monitoring security advisories can help prevent similar vulnerabilities.

Patching and Updates

The fix for this issue will be included in TensorFlow 2.5.0, with patches cherrypicked for TensorFlow 2.4.2 and TensorFlow 2.3.3.