title: CBC padding oracle in AWS S3 Crypto SDK for GoLang
description: 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), which then allows an attacker who has write access to the target's S3 bucket and can observe whether or not an endpoint with access to the key can decrypt a file, they can reconstruct the plaintext with (on average) 128*length (plaintext) queries to the endpoint, by exploiting CBC's ability to manipulate the bytes of the next block and PKCS5 padding errors. It is recommended to update your SDK to V2 or later, and re-encrypt your files.
problem types: CWE-327 Use of a Broken or Risky Cryptographic Algorithm
affected:
{
product: AWS S3 Crypto SDK for GoLang
vendor: Google LLC
versions:
lessThanOrEqual: V1, status: affected, version: stable, versionType: custom
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: LOCAL
availabilityImpact: NONE
baseScore: 5.6
baseSeverity: MEDIUM
confidentialityImpact: HIGH
integrityImpact: NONE
privilegesRequired: LOW
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
version: 3.1
]