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Debian LTS Advisory DLA-2596-1                [email protected]
https://www.debian.org/lts/security/                      Sylvain Beucler
March 17, 2021                                https://wiki.debian.org/LTS
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Package        : shadow
Version        : 1:4.4-4.1+deb9u1
CVE ID         : CVE-2017-12424 CVE-2017-20002
Debian Bug     : 756630 914957

Several vulnerabilities were discovered in the shadow suite of login
tools. An attacker may escalate privileges in specific configurations.


    Shadow incorrectly lists pts/0 and pts/1 as physical terminals in
    /etc/securetty. This allows local users to login as password-less
    users even if they are connected by non-physical means such as SSH
    (hence bypassing PAM's nullok_secure configuration). This notably
    affects environments such as virtual machines automatically
    generated with a default blank root password, allowing all local
    users to escalate privileges. It should be noted however that
    /etc/securetty will be dropped in Debian 11/bullseye.


    The newusers tool could be made to manipulate internal data
    structures in ways unintended by the authors. Malformed input may
    lead to crashes (with a buffer overflow or other memory
    corruption) or other unspecified behaviors. This crosses a
    privilege boundary in, for example, certain web-hosting
    environments in which a Control Panel allows an unprivileged user
    account to create subaccounts.

For Debian 9 stretch, these problems have been fixed in version

We recommend that you upgrade your shadow packages.

For the detailed security status of shadow please refer to
its security tracker page at:

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS