CVE-2020-1638
Junos OS & Junos OS Evolved: A specific IPv4 packet can lead to FPC restart.
- Published
- Updated
- Reserved
- Assigned by
- juniper
Description
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.
Timeline
ID reserved
By juniper
- 5 months later
· 5 months later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| juniperCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 1.3% · top 29% of all CVEs (7 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Weakness
Affected products
- affected 19.2 – < 19.2R1-S4, 19.2R2
- affected 19.3 – < 19.3R2-S2, 19.3R3
- affected 19.4 – < 19.4R1-S1, 19.4R2
- unaffected unspecified – < 19.2R1
Juniper Networks · Junos OS Evolved
- affected 19.2-EVO
- affected 19.3-EVO 19.2-EVO
- affected 19.4-EVO – < 19.4R2-EVO
Juniper Networks · Junos OS Evolved
- unaffected unspecified – < 19.2R1-EVO
What to do
Solution: The following software releases have been updated to resolve this specific issue: Junos OS: 19.2R1-S4, 19.2R2, 19.3R2-S2, 19.3R3, 19.4R1-S1, 19.4R2, 20.1R1, and all subsequent releases. Junos OS Evolved: 19.4R2-EVO, 20.1R1-EVO, and all subsequent releases.
Workaround: There is no workaround for this issue. Standard security best common practices such as limiting packet toward the RE only from trusted networks/host using firewall filter in combination with source address anti-spoofing should be applied to reduce the risk of exposure.
Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
References (1)
- https://kb.juniper.net/JSA11019 (opens in a new tab)x_refsource_CONFIRMx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2020-1638)Record last updated .