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Gentoo Linux Security Advisory                           GLSA 202105-11
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                                            https://security.gentoo.org/
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  Severity: Normal
     Title: GNU Screen: User-assisted execution of arbitrary code
      Date: May 26, 2021
      Bugs: #769770
        ID: 202105-11

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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/