CVE-2026-21921 Details
A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS).

When telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered.

This issue affects:

 Junos OS: 



* all versions before 22.4R3-S8,
* 23.2 versions before 23.2R2-S5,
* 23.4 versions before 23.4R2;




Junos OS Evolved:



* all versions before 22.4R3-S8-EVO,
* 23.2 versions before 23.2R2-S5-EVO,
* 23.4 versions before 23.4R2-EVO.
View at NVD
Exploit prediction scoring system (EPSS) score for CVE-2026-21921
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.04 Probability of exploitation activity being observed over the next 30 days (12th percentile)
CVSS score for CVE-2026-21921
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
6.5 Medium
Products affected by CVE-2026-21921
Junos 12.1x44
Junos 12.1x45
Junos 12.1x46
Junos 12.1x47
Junos 12.3x48
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
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CVE-2026-21921 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
NA 5 25.00%
ZM 4 20.00%
CN 2 10.00%
TW 2 10.00%
US 2 10.00%
VE 2 10.00%
KR 1 5.00%
NG 1 5.00%
VN 1 5.00%

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CVE-2026-21921 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Telecommunications 11 91.67%
Technology 1 8.33%

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