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 expected type when doing a RSA based key exchange allowing a malicious TLS server to cause a TLS client to panic.

Overview

Severity

Medium (CVSS 6.5)

CVSS Vector

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

Exploit Status

Not Exploited

Patch Tuesday

2021-Jul

Released

2021-07-31

EPSS Score

0.92% (percentile: 75.9%)

FAQ

Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability? One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information. If impact to additional products is identified, we will update the CVE to reflect this.

Detection & Weaponization (1 sources)

Maturity: Exploit

• GitHub PoC: 1 repositories

Affected Products (1)

Other

• 19007-16820

Revision History

• 2021-07-31: Information published.