CVE-2021-21401 Explained : Impact and Mitigation

Nanopb before versions 0.3.9.8 and 0.4.5 has a vulnerability that could lead to invalid

free()

or

realloc()

calls due to decoding a specially crafted message. It affects versions >= 0.3.2 and <= 0.3.9.7, and >= 0.4.0 and <= 0.4.4. The issue arises when a message type includes an

oneof

field containing both a pointer and a non-pointer field, leading to incorrect handling of field data. The impact is considered high with a CVSS base score of 7.1.

Understanding CVE-2021-21401

This section delves deeper into the nature of the vulnerability and its implications.

What is CVE-2021-21401?

In Nanopb versions 0.3.9.8 and 0.4.5, a specific input can trigger memory management issues, potentially leading to crashes or unauthorized access.

The Impact of CVE-2021-21401

The vulnerability could allow an attacker to supply malicious data that would be incorrectly processed, resulting in memory corruption and exploitation.

Technical Details of CVE-2021-21401

This section provides more technical insights into the CVE.

Vulnerability Description

The issue occurs due to the mishandling of

oneof

field data, causing memory-related functions to be called with incorrect parameters.

Affected Systems and Versions

Versions of Nanopb from 0.3.2 to 0.3.9.7, and 0.4.0 to 0.4.4 are impacted by this vulnerability.

Exploitation Mechanism

An attacker can exploit this issue by crafting a specific message format that triggers the mishandling of field data.

Mitigation and Prevention

To secure systems from CVE-2021-21401, immediate actions and long-term security practices are crucial.

Immediate Steps to Take

Users should update Nanopb to versions 0.3.9.8 or 0.4.5 to mitigate the vulnerability. Avoid parsing untrusted data until the patch is applied.

Long-Term Security Practices

Developers should implement secure coding practices and regularly update software to prevent similar vulnerabilities.

Patching and Updates

Refer to the GitHub Security Advisory for detailed information, workarounds, and the fixed versions.