Arch Linux Security Advisory ASA-202107-42
=========================================
Severity: Low
Date    : 2021-07-20
CVE-ID  : CVE-2021-34558
Package : go
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-2147

Summary
======
The package go before version 2:1.16.6-1 is vulnerable to denial of
service.

Resolution
=========
Upgrade to 2:1.16.6-1.

# pacman -Syu "go>=2:1.16.6-1"

The problem has been fixed upstream in version 1.16.6.

Workaround
=========
Clients that disable all TLS_RSA cipher suites (that is, TLS 1.0–1.2
cipher suites without ECDHE), as well as TLS 1.3-only clients, are
unaffected.

Description
==========
A security issue has been found in Go before version 1.16.6. crypto/tls
clients can panic when provided a certificate of the wrong type for the
negotiated parameters. net/http clients performing HTTPS requests are
also affected. The panic can be triggered by an attacker in a
privileged network position without access to the server certificate's
private key, as long as a trusted ECDSA or Ed25519 certificate for the
server exists (or can be issued), or the client is configured with
Config.InsecureSkipVerify. Clients that disable all TLS_RSA cipher
suites (that is, TLS 1.0–1.2 cipher suites without ECDHE), as well as
TLS 1.3-only clients, are unaffected.

Impact
=====
A man-in-the-middle attacker able to intercept a TLS negotiation could
crash a TLS client by injecting a crafted invalid certificate.

References
=========
https://groups.google.com/g/golang-announce/c/n9FxMelZGAQ/m/4ZhvTx0dAQAJ
https://github.com/golang/go/issues/47143
https://github.com/golang/go/commit/58bc454a11d4b3dbc03f44dfcabb9068a9c076f4
https://security.archlinux.org/CVE-2021-34558