CVE-2020-1638 | Junos OS & Junos OS Evolved: A specific IPv4 packet can lead to FPC restart.

The FPC (Flexible PIC Concentrator) of Juniper Networks Junos OS and Junos OS Evolved may restart after processing a specific IPv4 packet. Only packets destined to the device itself, successfully reaching the RE through existing edge and control plane filtering, will be able to cause the FPC restart. When this issue occurs, all traffic via the FPC will be dropped. By continuously sending this specific IPv4 packet, an attacker can repeatedly crash the FPC, causing an extended Denial of Service (DoS) condition. This issue can only occur when processing a specific IPv4 packet. IPv6 packets cannot trigger this issue. This issue affects: Juniper Networks Junos OS on MX Series with MPC10E or MPC11E and PTX10001: 19.2 versions prior to 19.2R1-S4, 19.2R2; 19.3 versions prior to 19.3R2-S2, 19.3R3; 19.4 versions prior to 19.4R1-S1, 19.4R2. Juniper Networks Junos OS Evolved on on QFX5220, and PTX10003 series: 19.2-EVO versions; 19.3-EVO versions; 19.4-EVO versions prior to 19.4R2-EVO. This issue does not affect Junos OS versions prior to 19.2R1. This issue does not affect Junos OS Evolved versions prior to 19.2R1-EVO.

Published: 2020-04-08 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-1638 is rated Moderate Risk (49.8/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.39%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-1638

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 0.61% 0.39% -0.22%
2 2025-03-29 0.39% 0.61% +0.22%
3 2025-03-17 — 0.39% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-1638

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2020-1638

Affected software / configurations for CVE-2020-1638

Vendor Product Version Raw CPE
juniper junos 19.2 cpe:2.3:o:juniper:junos:19.2:-:*:*:*:*:*:*
juniper junos 19.2 cpe:2.3:o:juniper:junos:19.2:r1:*:*:*:*:*:*
juniper junos 19.2 cpe:2.3:o:juniper:junos:19.2:r1-s1:*:*:*:*:*:*
juniper junos 19.2 cpe:2.3:o:juniper:junos:19.2:r1-s2:*:*:*:*:*:*
juniper junos 19.2 cpe:2.3:o:juniper:junos:19.2:r1-s3:*:*:*:*:*:*
juniper junos 19.3 cpe:2.3:o:juniper:junos:19.3:r1:*:*:*:*:*:*
juniper junos 19.3 cpe:2.3:o:juniper:junos:19.3:r1-s1:*:*:*:*:*:*
juniper junos 19.3 cpe:2.3:o:juniper:junos:19.3:r2:*:*:*:*:*:*
juniper junos 19.3 cpe:2.3:o:juniper:junos:19.3:r2-s1:*:*:*:*:*:*
juniper junos 19.4 cpe:2.3:o:juniper:junos:19.4:r1:*:*:*:*:*:*
juniper junos_os_evolved 19.2 cpe:2.3:o:juniper:junos_os_evolved:19.2:r1:*:*:*:*:*:*
juniper junos_os_evolved 19.3 cpe:2.3:o:juniper:junos_os_evolved:19.3:r2:*:*:*:*:*:*
juniper junos_os_evolved 19.4 cpe:2.3:o:juniper:junos_os_evolved:19.4:r1:*:*:*:*:*:*

References for CVE-2020-1638

URL Tags
https://kb.juniper.net/JSA11019 Vendor Advisory
cvelogic Threat Intelligence