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Fencer Vulns
medium 6.5

CVE-2021-0237 json

Junos OS: EX4300-MP/EX4600/EX4650/QFX5K Series: Packet Forwarding Engine manager (FXPC) process crashes when deployed in a Virtual Chassis (VC) configuration

published 2021-04-22 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-2856

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 32%
public exploits
0
none known

Summary

On Juniper Networks EX4300-MP Series, EX4600 Series, EX4650 Series, QFX5K Series deployed as a Virtual Chassis with a specific Layer 2 circuit configuration, Packet Forwarding Engine manager (FXPC) process may crash and restart upon receipt of specific layer 2 frames. Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS on EX4300-MP Series, EX4600 Series, EX4650 Series, QFX5K Series 15.1 versions prior to 15.1R7-S9; 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R2-S13, 17.4R3-S4, 17.4R3-S5; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R2-S7, 18.4R3-S6; 19.1 versions prior to 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R2-S4, 19.4R3-S1; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2, 20.2R3; 20.3 versions prior to 20.3R1-S2, 20.3R2;

Patch / fix

  • Juniper Networks Junos OS 15.1R7-S9, 17.3R3-S11, 17.4R2-S13, 17.4R3-S4, 17.4R3-S5, 18.2R3-S8, 18.3R3-S4, 18.4R2-S7, 18.4R3-S6, 19.1R3-S4, 19.2R1-S6, 19.2R3-S1, 19.3R3-S1, 19.4R2-S4, 19.4R3-S1, 20.1R2, 20.2R2, 20.2R3, 20.3R1-S2, 20.3R2

Exploit prediction

0.38% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 3.3 AV:A/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • Juniper Networks Junos OS

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.