Vulnerability · Published Jan 15, 2026 · Assigned by juniper

CVE-2026-21920Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash

High 7.5

In plain English

A high-severity security flaw in Junos OS from Juniper Networks. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 58.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
Juniper Networks	Junos OS	23.4 – before 23.4R2-S524.2 – before 24.2R2-S124.4 – before 24.4R2

Weakness: CWE-252 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://supportportal.juniper.net/JSA106020 vendor-advisory
https://kb.juniper.net/JSA106020 vendor-advisory