CVE-2020-8911 Explained : Impact and Mitigation

A padding oracle vulnerability exists in the AWS S3 Crypto SDK for GoLang versions prior to V2. The SDK allows users to encrypt files with AES-CBC without computing a Message Authentication Code (MAC), potentially leading to plaintext reconstruction by attackers. Update to V2 or later to mitigate the risk.

Understanding CVE-2020-8911

This CVE involves a CBC padding oracle vulnerability in the AWS S3 Crypto SDK for GoLang.

What is CVE-2020-8911?

This vulnerability allows attackers to reconstruct plaintext by exploiting AES-CBC encryption without a Message Authentication Code (MAC) in the SDK.

The Impact of CVE-2020-8911

CVSS Base Score: 5.6 (Medium Severity)
Confidentiality Impact: High
Attack Complexity: High
Privileges Required: Low
Scope: Changed
Vector String: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

Technical Details of CVE-2020-8911

The technical details of the vulnerability in the AWS S3 Crypto SDK for GoLang.

Vulnerability Description

The SDK allows encryption without a MAC, enabling attackers to reconstruct plaintext.

Affected Systems and Versions

Affected Product: AWS S3 Crypto SDK for GoLang
Vendor: Google LLC
Affected Versions: <= V1 (stable, custom version)

Exploitation Mechanism

Attackers with write access to the S3 bucket can observe decryption attempts to reconstruct plaintext.

Mitigation and Prevention

Steps to mitigate and prevent exploitation of CVE-2020-8911.

Immediate Steps to Take

Update the SDK to V2 or later.
Re-encrypt all files using the updated SDK.

Long-Term Security Practices

Implement secure encryption practices.
Regularly review and update cryptographic algorithms.

Patching and Updates

Stay informed about security advisories and update the SDK promptly.