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AUSCERT Security Bulletin
ASB-2019.0136
Alpine Linux Docker Image root User Hard-Coded Credential Vulnerability
9 May 2019
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AusCERT Security Bulletin Summary
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Product: Alpine Linux Docker Image
Operating System: Alpine Linux
Impact/Access: Root Compromise -- Remote/Unauthenticated
Resolution: Mitigation
CVE Names: CVE-2019-5021
Member content until: Saturday, June 8 2019
OVERVIEW
A hard-coded root credential vulnerability has been discovered in the
official Alpine Linux Docker images since version 3.3 [1]
IMPACT
Cisco Talos has provided the following information:
"Versions of the Official Alpine Linux Docker images (since v3.3)
contain a NULL password for the root user. This vulnerability appears to
be the result of a regression introduced in December t2015. Due to the
nature of this issue, systems deployed using affected versions of the
Alpine Linux container that utilize Linux PAM, or some other mechanism
that uses the system shadow file as an authentication database, may
accept a NULL password for the root user." [1]
MITIGATION
Cisco Talos have provided the following advice:
"The root account should be explicitly disabled in Docker images built
using affected versions as a base. The likelihood of exploitation of
this vulnerability is environment-dependent, as successful exploitation
requires that an exposed service or application utilise Linux PAM, or
some other mechanism which uses the system shadow file as an
authentication database." [1]
REFERENCES
[1] Alpine Linux Docker Image root User Hard-Coded Credential
Vulnerability
https://talosintelligence.com/vulnerability_reports/TALOS-2019-0782
AusCERT has made every effort to ensure that the information contained
in this document is accurate. However, the decision to use the information
described is the responsibility of each user or organisation. The decision to
follow or act on information or advice contained in this security bulletin is
the responsibility of each user or organisation, and should be considered in
accordance with your organisation's site policies and procedures. AusCERT
takes no responsibility for consequences which may arise from following or
acting on information or advice contained in this security bulletin.
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Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
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