Vulnerability Details CVE-2026-21920
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 16.6%
CVSS Severity
CVSS v3 Score 7.5
Products affected by CVE-2026-21920
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cpe:2.3:h:juniper:srx1500:-
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cpe:2.3:h:juniper:srx1600:-
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cpe:2.3:h:juniper:srx2300:-
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cpe:2.3:h:juniper:srx300:-
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cpe:2.3:h:juniper:srx320:-
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cpe:2.3:h:juniper:srx340:-
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cpe:2.3:h:juniper:srx345:-
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cpe:2.3:h:juniper:srx380:-
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cpe:2.3:h:juniper:srx4100:-
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cpe:2.3:h:juniper:srx4120:-
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cpe:2.3:h:juniper:srx4200:-
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cpe:2.3:h:juniper:srx4300:-
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cpe:2.3:h:juniper:srx4600:-
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cpe:2.3:h:juniper:srx4700:-
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cpe:2.3:h:juniper:srx5400:-
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cpe:2.3:h:juniper:srx5600:-
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cpe:2.3:h:juniper:srx5800:-
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cpe:2.3:o:juniper:junos:23.4
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cpe:2.3:o:juniper:junos:24.2
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cpe:2.3:o:juniper:junos:24.4