title: Junos OS: EX4300: Stateless firewall policer fails to discard traffic
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.
problem types: CWE-241 Improper Handling of Unexpected Data Type
affected:
{
platforms: EX4300
product: Junos OS
vendor: Juniper Networks
versions:
lessThan: 17.3R3-S10, status: affected, version: unspecified, versionType: custom
lessThan: 17.4R3-S3, status: affected, version: 17.4, versionType: custom
lessThan: 18.1R3-S11, status: affected, version: 18.1, versionType: custom
lessThan: 18.2R3-S6, status: affected, version: 18.2, versionType: custom
lessThan: 18.3R3-S4, status: affected, version: 18.3, versionType: custom
lessThan: 18.4R3-S6, status: affected, version: 18.4, versionType: custom
lessThan: 19.1R3-S3, status: affected, version: 19.1, versionType: custom
lessThan: 19.2R3-S1, status: affected, version: 19.2, versionType: custom
lessThan: 19.3R3-S1, status: affected, version: 19.3, versionType: custom
lessThan: 19.4R3, status: affected, version: 19.4, versionType: custom
lessThan: 20.1R2, status: affected, version: 20.1, versionType: custom
lessThan: 20.2R2, status: affected, version: 20.2, versionType: custom
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: ADJACENT_NETWORK
availabilityImpact: LOW
baseScore: 4.7
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: NONE
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
version: 3.1
]
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: Junos OS 17.3R3-S10, 17.4R3-S3, 18.1R3-S11, 18.2R3-S6, 18.3R3-S4, 18.4R3-S6, 19.1R3-S3, 19.2R3-S1, 19.3R3-S1, 19.4R3, 20.1R2, 20.2R2, 20.3R1, and all subsequent releases.
workarounds: There are no viable workarounds for this issue.