Arch Linux Security Advisory ASA-202106-6
========================================
Severity: High
Date    : 2021-06-01
CVE-ID  : CVE-2021-22898 CVE-2021-22901
Package : libcurl-compat
Type    : multiple issues
Remote  : Yes
Link    : https://security.archlinux.org/AVG-1997

Summary
======
The package libcurl-compat before version 7.77.0-1 is vulnerable to
multiple issues including arbitrary code execution and information
disclosure.

Resolution
=========
Upgrade to 7.77.0-1.

# pacman -Syu "libcurl-compat>=7.77.0-1"

The problems have been fixed upstream in version 7.77.0.

Workaround
=========
- CVE-2021-22898 can be mitigated by avoiding to use the -t command
line option and CURLOPT_TELNETOPTIONS.
- No known workaround exists for CVE-2021-22901.

Description
==========
- CVE-2021-22898 (information disclosure)

A security issue has been found in curl before version 7.77.0. curl
supports the -t command line option, known as CURLOPT_TELNETOPTIONS in
libcurl. This rarely used option is used to send variable=content pairsto TELNET servers. Due to flaw in the option parser for sending NEW_ENV
variables, libcurl could be made to pass on uninitialized data from a
stack based buffer to the server. Therefore potentially revealing
sensitive internal information to the server using a clear-text network
protocol.

- CVE-2021-22901 (arbitrary code execution)

libcurl before version 7.77.0 can be tricked into using already freed
memory when a new TLS session is negotiated or a client certificate is
requested on an existing connection. For example, this can happen when
a TLS server requests a client certificate on a connection that was
established without one. A malicious server can use this in rare
unfortunate circumstances to potentially reach remote code execution in
the client. The flaw can only happen in libcurl built to use OpenSSL.

Impact
=====
curl could disclose potentially sensitive memory information to a
remote server over Telnet when an uncommon option is used.
Additionally, a remote attacker could cause arbitrary code execution
through a crafted TLS handshake.

References
=========
https://curl.se/docs/CVE-2021-22898.html
https://github.com/curl/curl/commit/39ce47f219b09c380b81f89fe54ac586c8db6bde
https://curl.se/docs/CVE-2021-22901.html
https://github.com/curl/curl/commit/7f4a9a9b2a49547eae24d2e19bc5c346e9026479
https://security.archlinux.org/CVE-2021-22898
https://security.archlinux.org/CVE-2021-22901