Out-of-bounds read in HTTP client no_proxy handling

Issue summary: An application using the OpenSSL HTTP client API functions may

trigger an out-of-bounds read if the 'no_proxy' environment variable is set and

the host portion of the authority component of the HTTP URL is an IPv6 address.

Impact summary: An out-of-bounds read can trigger a crash which leads to

Denial of Service for an application.

The OpenSSL HTTP client API functions can be used directly by applications

but they are also used by the OCSP client functions and CMP (Certificate

Management Protocol) client implementation in OpenSSL. However the URLs used

by these implementations are unlikely to be controlled by an attacker.

In this vulnerable code the out of bounds read can only trigger a crash.

Furthermore the vulnerability requires an attacker-controlled URL to be

passed from an application to the OpenSSL function and the user has to have

a 'no_proxy' environment variable set. For the aforementioned reasons the

issue was assessed as Low severity.

The vulnerable code was introduced in the following patch releases:

3.0.16, 3.1.8, 3.2.4, 3.3.3, 3.4.0 and 3.5.0.

The FIPS modules in 3.5, 3.4, 3.3, 3.2, 3.1 and 3.0 are not affected by this

issue, as the HTTP client implementation is outside the OpenSSL FIPS module

boundary.