CVE-2021-0243 Information

Description

Improper Handling of Unexpected Data in the firewall policer of Juniper Networks Junos OS on EX4300 switches allows matching traffic to exceed set policer limits possibly leading to a limited Denial of Service (DoS) condition. When the firewall policer discard action fails on a Layer 2 port it will allow traffic to pass even though it exceeds set policer limits. Traffic will not get discarded and will be forwarded even though a policer discard action is configured. When the issue occurs traffic is not discarded as desired which can be observed by comparing the Input bytes with the Output bytes using the following command: user@junos> monitor interface traffic Interface Link Input bytes (bps) Output bytes (bps) ge-0/0/0 Up 37425422 (82616) 37425354 (82616) «« egress ge-0/0/1 Up 37425898 (82616) 37425354 (82616) «« ingress The expected output with input and output counters differing is shown below: Interface Link Input bytes (bps) Output bytes (bps) ge-0/0/0 Up 342420570 (54600) 342422760 (54600) «« egress ge-0/0/1 Up 517672120 (84000) 342420570 (54600) «« ingress This issue only affects IPv4 policing. IPv6 traffic and firewall policing actions are not affected by this issue. This issue affects Juniper Networks Junos OS on the EX4300: All versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S6; 19.1 versions prior to 19.1R3-S3; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2.

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

Reference

https://kb.juniper.net/JSA11136

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

CHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

LOW

Base Severity

4.7