Main Vulnerability Database SB2026012023

SB2026012023 - Unchecked Return Value in Juniper Junos OS

Published: January 20, 2026

Security Bulletin ID SB2026012023

CSH Severity

Medium

Patch available

YES

Number of vulnerabilities 1

Exploitation vector Remote access

Highest impact Denial of service

Breakdown by Severity

Low
Medium
High
Critical

Description

This security bulletin contains information about 1 vulnerability.

1) Unchecked Return Value (CVE-ID: CVE-2026-21920)

CWE-ID: CWE-252 - Unchecked Return Value

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to unchecked return value error in the DNS module. A remote non-authenticated attacker can 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.

Remediation

Install update from vendor's website.

References

https://supportportal.juniper.net/s/article/2026-01-Security-Bulletin-Junos-OS-SRX-Series-If-a-specific-request-is-processed-by-the-DNS-subsystem-flowd-will-crash-CVE-2026-21920