CVE-2021-31351
No exploitation reported by the sources we read.
- Published2021-10-19
- WeaknessCWE-754
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
An Improper Check for Unusual or Exceptional Conditions in packet processing on the MS-MPC/MS-MIC utilized by Juniper Networks Junos OS allows a malicious attacker to send a specific packet, triggering the MS-MPC/MS-MIC to reset, causing a Denial of Service (DoS). Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects specific versions of Juniper Networks Junos OS on MX Series: 17.3R3-S11; 17.4R2-S13; 17.4R3 prior to 17.4R3-S5; 18.1R3-S12; 18.2R2-S8, 18.2R3-S7, 18.2R3-S8; 18.3R3-S4; 18.4R3-S7; 19.1R3-S4, 19.1R3-S5; 19.2R1-S6; 19.3R3-S2; 19.4R2-S4, 19.4R2-S5; 19.4R3-S2; 20.1R2-S1; 20.2R2-S2, 20.2R2-S3, 20.2R3; 20.3R2, 20.3R2-S1; 20.4R1, 20.4R1-S1, 20.4R2; 21.1R1; This issue does not affect any version of Juniper Networks Junos OS prior to 15.1X49-D240;
Timeline
dates in UTC- 2021-10-1919:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-31351?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-31351?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 17.3 | = 17.3 | no fix published | NVD |
| 17.4 | = 17.4 | no fix published | NVD |
| 18.1 | = 18.1 | no fix published | NVD |
| 18.2 | = 18.2 | no fix published | NVD |
| 18.3 | = 18.3 | no fix published | NVD |
| 18.4 | = 18.4 | no fix published | NVD |
| 19.1 | = 19.1 | no fix published | NVD |
| 19.2 | = 19.2 | no fix published | NVD |
| 19.3 | = 19.3 | no fix published | NVD |
| 19.4 | = 19.4 | no fix published | NVD |
| 20.1 | = 20.1 | no fix published | NVD |
| 20.2 | = 20.2 | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
Advisories and patches
- kb.juniper.netVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- CNACVSS 3.17.5read 2026-10-23
- NVDCVSS 2.05read 2026-10-23
- CNAweakness (CWE)CWE-754read 2026-10-23
- NVDweakness (CWE)CWE-754read 2026-10-23
- FIRST EPSSEPSS score1.0 %2026-10-22
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2021-10-19
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-31351?
Is CVE-2021-31351 actively exploited?
What is the CVSS score for CVE-2021-31351?
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