CVE-2026-21920
Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash
- State
- Published
- Severity
- 8.7 High
- Published
- Jan 15, 2026
- Updated
- Jan 15, 2026
- Reserved
- Jan 5, 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | 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 | juniper |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | juniper |
Weaknesses
- CWE-252 Unchecked Return Value
Affected Products
| Product | Versions |
|---|---|
Junos OSJuniper Networks |
|
References
- https://supportportal.juniper.net/JSA106020vendor-advisory
- https://kb.juniper.net/JSA106020vendor-advisory
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