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AUSCERT External Security Bulletin Redistribution
ESB-2020.3738.2
JSA11082 - 2020-10 Security Bulletin: Junos OS: EX4600, QFX5K Series:
Stateless firewall filter matching 'user-vlan-id' will cause
incomplete discard action (CVE-2020-1685)
2 November 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: Junos OS
Publisher: Juniper Networks
Operating System: Juniper
Impact/Access: Unauthorised Access -- Remote/Unauthenticated
Reduced Security -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-1685
Original Bulletin:
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA11082
Revision History: November 2 2020: modified formating
October 29 2020: Initial Release
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2020-10 Security Bulletin: Junos OS: EX4600, QFX5K Series: Stateless firewall filter matching 'user-vlan-id' will cause incomplete discard action (CVE-2020-1685)
Article ID : JSA11082
Last Updated: 28 Oct 2020
Version : 2.0
Product Affected:
This issue affects Junos OS 18.1, 18.2, 18.3, 18.4, 19.1, 19.2. Affected
platforms: EX4600, QFX5K Series.
Problem:
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:
o 18.1 versions prior to 18.1R3-S7, except 18.1R3;
o 18.2 versions prior to 18.2R2-S7, 18.2R3-S1;
o 18.3 versions prior to 18.3R1-S5, 18.3R2-S4, 18.3R3;
o 18.4 versions prior to 18.4R1-S7, 18.4R2-S1, 18.4R3;
o 19.1 versions prior to 19.1R1-S5, 19.1R2;
o 19.2 versions prior to 19.2R1-S5, 19.2R2.
A sample VXLAN configuration is shown below:
evpn {
encapsulation vxlan;
}
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was found during internal product security testing or research.
This issue has been assigned CVE-2020-1685 .
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.
This issue is being tracked as 1446489 .
Workaround:
Avoid using the user-vlan-id match criteria.
Implementation:
Software releases or updates are available for download at https://
www.juniper.net/support/downloads/ .
Modification History:
2020-10-14: Initial Publication
CVSS Score:
5.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N)
Severity Level:
Medium
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common
Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."
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