Junos OS: EX4600, QFX5K Series: Stateless firewall filter matching 'user-vlan-id' will cause incomplete discard action

Description

When configuring stateless firewall filters in Juniper Networks EX4600 and QFX 5000 Series devices using Virtual Extensible LAN protocol (VXLAN), the discard action will fail to discard traffic under certain conditions. Given a firewall filter configuration similar to: family ethernet-switching { filter L2-VLAN { term ALLOW { from { user-vlan-id 100; } then { accept; } } term NON-MATCH { then { discard; } } when there is only one term containing a 'user-vlan-id' match condition, and no other terms in the firewall filter except discard, the discard action for non-matching traffic will only discard traffic with the same VLAN ID specified under 'user-vlan-id'. Other traffic (e.g. VLAN ID 200) will not be discarded. This unexpected behavior can lead to unintended traffic passing through the interface where the firewall filter is applied. This issue only affects systems using VXLANs. This issue affects Juniper Networks Junos OS on QFX5K Series: 18.1 versions prior to 18.1R3-S7, except 18.1R3; 18.2 versions prior to 18.2R2-S7, 18.2R3-S1; 18.3 versions prior to 18.3R1-S5, 18.3R2-S4, 18.3R3; 18.4 versions prior to 18.4R1-S7, 18.4R2-S1, 18.4R3; 19.1 versions prior to 19.1R1-S5, 19.1R2; 19.2 versions prior to 19.2R1-S5, 19.2R2.

Scores

EPSS (exploitation in 30 days)

0.76% · top 45% of all CVEs (5 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.8.

Weakness

• CWE-203 Information Exposure Through Discrepancy (opens in a new tab)All about CWE-203 and its CVEs

Affected products

• Juniper Networks · Junos OS

  • unaffected 18.1R3
  • affected 18.1 – < 18.1R3-S7
  • affected 18.2 – < 18.2R2-S7, 18.2R3-S1
  • affected 18.3 – < 18.3R1-S5, 18.3R2-S4, 18.3R3
  • affected 18.4 – < 18.4R1-S7, 18.4R2-S1, 18.4R3
  • affected 19.1 – < 19.1R1-S5, 19.1R2
  • affected 19.2 – < 19.2R1-S5, 19.2R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS 18.1R3-S7, 18.2R2-S7, 18.2R3-S1, 18.3R1-S5, 18.3R2-S4, 18.3R3, 18.4R1-S7, 18.4R2-S1, 18.4R3, 19.1R1-S5, 19.1R2, 19.2R1-S5, 19.2R2, 19.3R1, and all subsequent releases.

Workaround: Avoid using the user-vlan-id match criteria.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

• https://kb.juniper.net/JSA11082 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2020-1685](https://trackcve.app/badge/CVE-2020-1685.svg)](https://trackcve.app/cve/CVE-2020-1685)

Record last updated 16 Sept 2024, 20:12 UTC.