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High severity7.5NVD Advisory· Published Jan 15, 2026· Updated Jun 17, 2026

CVE-2026-21920

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

20
  • Juniper Networks/Junos19 versions
    cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*+ 18 more
    • cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1:*:*:*:*:*:*
    • (no CPE)range: 23.4
  • Juniper Networks/Junos OS on SRX Seriesllm-fuzzy
    Range: <23.4R2-S5, <24.2R2-S1, <24.4R2

Patches

Vulnerability mechanics

References

2

News mentions

0

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