Mailing List Archive

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Gentoo Linux Security Advisory GLSA 202105-11
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
https://security.gentoo.org/
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Severity: Normal
Title: GNU Screen: User-assisted execution of arbitrary code
Date: May 26, 2021
Bugs: #769770
ID: 202105-11

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Synopsis
========

A vulnerability in GNU screen may allow a remote attacker to execute
arbitrary code.

Background
==========

GNU Screen is a full-screen window manager that multiplexes a physical
terminal between several processes, typically interactive shells.

Affected packages
=================

-------------------------------------------------------------------
Package / Vulnerable / Unaffected
-------------------------------------------------------------------
1 app-misc/screen < 4.8.0-r2 >= 4.8.0-r2

Description
===========

It was discovered that GNU screen did not properly handle certain UTF-8
character sequences.

Impact
======

A remote attacker could entice a user to run a program where attacker
controls the output inside a GNU screen session, possibly resulting in
execution of arbitrary code with the privileges of the process or a
Denial of Service condition.

Workaround
==========

This vulnerability can be mitigated by disabling UTF-8 processing in
.screenrc.

Resolution
==========

All GNU screen users should upgrade to the latest version:

# emerge --sync
# emerge --ask --oneshot --verbose ">=app-misc/screen-4.8.0-r2"

References
==========

[ 1 ] CVE-2021-26937
https://nvd.nist.gov/vuln/detail/CVE-2021-26937

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

https://security.gentoo.org/glsa/202105-11

Concerns?
=========

Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users' machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
https://bugs.gentoo.org.

License
=======

Copyright 2021 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

https://creativecommons.org/licenses/by-sa/2.5