CVE-2020-8911 CBC padding oracle in AWS S3 Crypto SDK for GoLang

2020-08-1119:20:14

CWE-327

Google

www.cve.org

5.6 Medium

CVSS3

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

5.8 Medium

AI Score

Confidence

High

0.001 Low

EPSS

Percentile

20.2%

JSON

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.

CNA Affected

[
  {
    "product": "AWS S3 Crypto SDK for GoLang",
    "vendor": "Google LLC",
    "versions": [
      {
        "lessThanOrEqual": "V1",
        "status": "affected",
        "version": "stable",
        "versionType": "custom"
      }
    ]
  }
]