Unrated severityNVD Advisory· Published Jan 15, 2026· Updated Jan 15, 2026
Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash
CVE-2026-21920
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
2- Range: >=23.4, <23.4R2-S5 or >=24.2, <24.2R2-S1 or >=24.4, <24.4R2
- Juniper Networks/Junos OSv5Range: 23.4
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
2- kb.juniper.net/JSA106020mitrevendor-advisory
- supportportal.juniper.net/JSA106020mitrevendor-advisory
News mentions
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