title: Junos OS: Insufficient validation of environment variables in telnet client may lead to stack-based buffer overflow
description: 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.
problem types: CWE-121 Stack-based Buffer Overflow
affected:
{
vendor: Juniper Networks
product: Junos OS
versions:
version: 12.3 versions prior to 12.3R12-S13, status: affected
version: 12.3X48 versions prior to 12.3X48-D80, status: affected
version: 14.1X53 versions prior to 14.1X53-D130 and 14.1X53-D49, status: affected
version: 15.1 versions prior to 15.1F6-S12 and15.1R7-S4, status: affected
version: 15.1X49 versions prior to 15.1X49-D170, status: affected
version: 15.1X53 versions prior to 15.1X53-D237 and 15.1X53-D496 and 15.1X53-D591 and 15.1X53-D69, status: affected
version: 16.1 versions prior to 16.1R3-S11 and 16.1R7-S4, status: affected
version: 16.2 versions prior to 16.2R2-S9, status: affected
version: 17.1 versions prior to 17.1R3, status: affected
version: 17.2 versions prior to 17.2R1-S8 and 17.2R2-S7 and 17.2R3-S1, status: affected
version: 17.3 versions prior to 17.3R3-S4, status: affected
version: 17.4 versions prior to 17.4R1-S6 and 17.4R2-S3 and 17.4R3, status: affected
version: 18.1 versions prior to 18.1R2-S4 and 18.1R3-S3, status: affected
version: 18.2 versions prior to 18.2R1-S5 and 18.2R2-S2 and 18.2R3, status: affected
version: 18.2X75 versions prior to 18.2X75-D40, status: affected
version: 18.3 versions prior to 18.3R1-S3 and 18.3R2, status: affected
version: 18.4 versions prior to 18.4R1-S2 and 18.4R2, status: affected
}
metrics:
cvssV3_0: [
version: 3.0
vectorString: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
attackVector: LOCAL
attackComplexity: LOW
privilegesRequired: LOW
userInteraction: NONE
scope: UNCHANGED
confidentialityImpact: HIGH
integrityImpact: HIGH
availabilityImpact: HIGH
baseScore: 7.8
baseSeverity: HIGH
]
exploits: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
solutions: 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.
workarounds: Since this issue is specific to outbound connections to a malicious host from the local telnet client, mitigation includes:
* limit access to the Junos CLI and shell from only from trusted administrators
* block outbound telnet connections
* deny access to the telnet command and shell per user or user class