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AUSCERT External Security Bulletin Redistribution
JSA11135 - 2021-04 Security Bulletin: Junos OS: EX4300: FPC crash upon
receipt of specific frames on an interface without L2PT or dot1x configured
19 April 2021
AusCERT Security Bulletin Summary
Product: Junos OS: EX4300
Publisher: Juniper Networks
Operating System: Juniper
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2021-0242
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2021-04 Security Bulletin: Junos OS: EX4300: FPC crash upon receipt of specific frames
on an interface without L2PT or dot1x configured (CVE-2021-0242)
Article ID : JSA11135
Last Updated: 16 Apr 2021
Version : 2.0
This issue affects Junos OS 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2,
19.3, 19.4, 20.1, 20.2, 20.3. Affected platforms: EX4300.
A vulnerability due to the improper handling of direct memory access (DMA)
buffers on EX4300 switches on Juniper Networks Junos OS allows an attacker
sending specific unicast frames to trigger a Denial of Service (DoS) condition
by exhausting DMA buffers, causing the FPC to crash and the device to restart.
The DMA buffer leak is seen when receiving these specific, valid unicast frames
on an interface without Layer 2 Protocol Tunneling (L2PT) or dot1x configured.
Interfaces with either L2PT or dot1x configured are not vulnerable to this
When this issue occurs, DMA buffer usage keeps increasing and the following
error log messages may be observed:
Apr 14 14:29:34.360 /kernel: pid 64476 (pfex_junos), uid 0: exited on signal 11
Apr 14 14:29:33.790 init: pfe-manager (PID 64476) terminated by signal number
11. Core dumped!
The DMA buffers on the FPC can be monitored by the executing vty command 'show
ID Base Total(b) Free(b) Used(b) % Name
- -- ---------- ----------- ----------- ----------- --- -----------
0 4a46000 268435456 238230496 30204960 11 Kernel
1 18a46000 67108864 17618536 49490328 73 Bcm_sdk
2 23737000 117440512 18414552 99025960 84 DMA buf <<<<< keeps increasing
3 2a737000 16777216 16777216 0 0 DMA desc
This issue affects Juniper Networks Junos OS on the EX4300:
o 17.3 versions prior to 17.3R3-S11;
o 17.4 versions prior to 17.4R2-S13, 17.4R3-S4;
o 18.1 versions prior to 18.1R3-S12;
o 18.2 versions prior to 18.2R2-S8, 18.2R3-S7;
o 18.3 versions prior to 18.3R3-S4;
o 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7;
o 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4;
o 19.2 versions prior to 19.2R1-S6, 19.2R3-S2;
o 19.3 versions prior to 19.3R3-S2;
o 19.4 versions prior to 19.4R2-S3, 19.4R3-S1;
o 20.1 versions prior to 20.1R2;
o 20.2 versions prior to 20.2R2-S1, 20.2R3;
o 20.3 versions prior to 20.3R1-S1, 20.3R2.
No specific configuration is required on the EX4300.
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was seen during production usage.
This issue has been assigned CVE-2021-0242 .
The following software releases have been updated to resolve this specific
issue: Junos OS 17.3R3-S11, 17.4R2-S13, 17.4R3-S4, 18.1R3-S12, 18.2R2-S8,
18.2R3-S7, 18.3R3-S4, 18.4R1-S8, 18.4R2-S7, 18.4R3-S7, 19.1R1-S6, 19.1R2-S2,
19.1R3-S4, 19.2R1-S6, 19.2R3-S2, 19.3R3-S2, 19.4R2-S3, 19.4R3-S1, 20.1R2,
20.2R2-S1, 20.2R3, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.
This issue is being tracked as 1545530 .
There are no known workarounds for this issue.
Software releases or updates are available for download at https://
2021-04-14: Initial Publication.
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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