Insufficient validation of environment variables in the telnet client supplied in Junos OS can lead to stack-based buffer overflows, which can be exploited to bypass veriexec restrictions on Junos OS. A stack-based overflow is present in the handling of environment variables when connecting via the telnet client to remote telnet servers.
This issue only affects the telnet client — accessible from the CLI or shell — in Junos OS. Inbound telnet services are not affected by this issue.
This issue affects Juniper Networks Junos OS:
- 12.3 versions prior to 12.3R12-S13;
- 12.3X48 versions prior to 12.3X48-D80;
- 14.1X53 versions prior to 14.1X53-D130, 14.1X53-D49;
- 15.1 versions prior to 15.1F6-S12, 15.1R7-S4;
- 15.1X49 versions prior to 15.1X49-D170;
- 15.1X53 versions prior to 15.1X53-D237, 15.1X53-D496, 15.1X53-D591, 15.1X53-D69;
- 16.1 versions prior to 16.1R3-S11, 16.1R7-S4;
- 16.2 versions prior to 16.2R2-S9;
- 17.1 versions prior to 17.1R3;
- 17.2 versions prior to 17.2R1-S8, 17.2R2-S7, 17.2R3-S1;
- 17.3 versions prior to 17.3R3-S4;
- 17.4 versions prior to 17.4R1-S6, 17.4R2-S3, 17.4R3;
- 18.1 versions prior to 18.1R2-S4, 18.1R3-S3;
- 18.2 versions prior to 18.2R1-S5, 18.2R2-S2, 18.2R3;
- 18.2X75 versions prior to 18.2X75-D40;
- 18.3 versions prior to 18.3R1-S3, 18.3R2;
- 18.4 versions prior to 18.4R1-S2, 18.4R2.
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was discovered during external security research.
This issue has been assigned CVE-2019-0053.
The following software releases have been updated to resolve this specific issue: 12.3R12-S13, 12.3X48-D80, 12.3X48-D85, 14.1X53-D130, 14.1X53-D49, 15.1F6-S12, 15.1R7-S4, 15.1X49-D170, 15.1X53-D237, 15.1X53-D496, 15.1X53-D591, 15.1X53-D69, 16.1R3-S11, 16.1R7-S4, 16.2R2-S9, 17.1R3, 17.2R1-S8, 17.2R2-S7, 17.2R3-S1, 17.3R3-S4, 17.4R1-S6, 17.4R2-S3, 17.4R3, 18.1R2-S4, 18.1R3-S3, 18.2R1-S5, 18.2R2-S2, 18.2R3, 18.2X75-D40, 18.3R1-S3, 18.3R2, 18.4R1-S2, 18.4R2, 19.1R1, and all subsequent releases.
This issue is being tracked as PR 1409847 which is visible on the Customer Support website.
Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).
Since this issue is specific to outbound telnet connections to a malicious host from the local telnet client, mitigation includes:
- limiting access to the Junos CLI and shell from only from trusted administrators
- blocking outbound telnet connections via a stateless firewall filter
- denying access to the '
telnet
' command and the Junos shell
Software Releases, patches and updates are available at
https://www.juniper.net/support/downloads/.
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."
The Juniper SIRT would like to would like to acknowledge and thank Matthew Hickey, Hacker House (
https://hacker.house/), who reported this issue on November 12, 2018.