# CVE-2026-21920

## Summary

- **CVE ID:** CVE-2026-21920
- **Severity:** HIGH
- **CVSS Score:** 8.7 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M)
- **CWE:** CWE-252
- **Published:** Jan 15, 2026
- **Last Modified:** Mar 12, 2026

## Description

An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).




If an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered.

This issue affects Junos OS on SRX Series:



  *  23.4 versions before 23.4R2-S5,
  *  24.2 versions before 24.2R2-S1,
  *  24.4 versions before 24.4R2.






This issue does not affect Junos OS versions before 23.4R1.

## Affected Products

- Juniper Networks — Junos OS (23.4)
- Juniper Networks — Junos OS (24.2)
- Juniper Networks — Junos OS (24.4)
- Juniper Networks — Junos OS (0)

## References

- [CNA](https://supportportal.juniper.net/JSA106020)
- [CNA](https://kb.juniper.net/JSA106020)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.46%
- **EPSS Percentile:** 38.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._