Strix
26.1K

CVE-2020-8911

MEDIUMCVSS 5.6/10EPSS 0.35%

Last modified

CVE-2020-8911 is a medium-severity vulnerability rated 5.6/10 on the CVSS scale. 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. EPSS estimates a 0.35% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
5.6/10

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

EPSS Probability
0.35%

26.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
AmazonAws S3 Crypto Sdk< 2.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2020-8911?
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.
How severe is CVE-2020-8911?
CVE-2020-8911 has a CVSS score of 5.6/10 (MEDIUM severity). The EPSS model estimates a 0.35% probability of exploitation in the next 30 days.
How do I fix CVE-2020-8911?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-8911?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST