CVE-2021-0264

Junos OS and Junos OS Evolved: MX Series with MPC10/MPC11, PTX10003, PTX10008: Line card may crash and restart when traffic is hitting a firewall filter having a term with syslog action configured

HIGH

7.5

CVSS Score

Published: April 22, 2021 at 07:37 PM UTC

Updated: June 17, 2026 at 03:29 AM UTC

22 products affected across 2 vendorsJunosJunos OS EvolvedMx960

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Severity

HIGH7.5

Exploit prediction

EPSS 1.0%

Description

A vulnerability in the processing of traffic matching a firewall filter containing a syslog action in Juniper Networks Junos OS on MX Series with MPC10/MPC11 cards installed, PTX10003 and PTX10008 Series devices, will cause the line card to crash and restart, creating a Denial of Service (DoS). Continued receipt and processing of packets matching the firewall filter can create a sustained Denial of Service (DoS) condition. When traffic hits the firewall filter, configured on lo0 or any physical interface on the line card, containing a term with a syslog action (e.g. 'term <name> then syslog'), the affected line card will crash and restart, impacting traffic processing through the ports of the line card. This issue only affects MX Series routers with MPC10 or MPC11 line cards, and PTX10003 or PTX10008 Series packet transport routers. No other platforms or models of line cards are affected by this issue. Note: This issue has also been identified and described in technical service bulletin TSB17931 (login required). This issue affects: Juniper Networks Junos OS on MX Series: 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S2, 20.2R3; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2. Juniper Networks Junos OS Evolved on PTX10003, PTX10008: All versions prior to 20.4R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 19.3R1.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos OS Evolved · Juniper

95%

18.3 r1 19.1 r1 19.1 r2 19.2 r1 19.2 r2 19.3 r1 19.3 r2 20.1 r1 20.1 r2 20.2 r1 20.2 r2 20.3 r1 20.3 r2 20.4 r1

juniper-ptx10003 (environment) · juniper-ptx10008 (environment)

Junos · Juniper Networks

95%

19.3 ≤ v < 19.3R3-S219.4 ≤ v < 19.4R3-S220.1 ≤ v < 20.1R320.2 ≤ v < 20.2R2-S2, 20.2R320.3 ≤ v < 20.3R320.4 ≤ v < 20.4R219.3 19.3 r1 19.3 r1-s1 19.3 r2 19.3 r2-s1 19.3 r2-s2 19.3 r2-s3 19.3 r2-s4 19.3 r2-s5 19.3 r3 19.4 19.4 r1 19.4 r1-s1 19.4 r1-s2 19.4 r2 19.4 r2-s1 19.4 r2-s2 19.4 r3 19.4 r3-s1 20.1 20.1 r1 20.1 r1-s1 20.1 r1-s2 20.1 r1-s3 20.1 r1-s4 20.1 r2 20.1 r2-s1 20.2 20.2 r1 20.2 r1-s1 20.2 r1-s2 20.2 r1-s3 20.2 r2 20.2 r2-s1 20.3 20.3 r1 20.3 r2 20.4 20.4 r1

Vendor states this is fixed in 19.3R1 (unaffected)

Affected range stops below 19.3R3-S2, so it looks safe — our inference, not a vendor statement

Affected range stops below 19.4R3-S2, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.1R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.2R2-S2, 20.2R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.3R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.4R2, so it looks safe — our inference, not a vendor statement

juniper-mx10 (environment) · juniper-mx10000 (environment) · juniper-mx10003 (environment) · juniper-mx10008 (environment) · juniper-mx10016 (environment) · juniper-mx104 (environment) · juniper-mx150 (environment) · juniper-mx2008 (environment) · juniper-mx2010 (environment) · juniper-mx2020 (environment) · juniper-mx204 (environment) · juniper-mx240 (environment) · juniper-mx40 (environment) · juniper-mx480 (environment) · juniper-mx5 (environment) · juniper-mx80 (environment) · juniper-mx960 (environment)

Junos OS Evolved · Juniper Networks

60%

v < 20.4R2-EVO

Affected range stops below 20.4R2-EVO, so it looks safe — our inference, not a vendor statement

Mx10 · Juniperdevice

80%

All versions

Mx10000 · Juniperdevice

80%

All versions

Mx10003 · Juniperdevice

80%