Improper Validation of Syntactic Correctness of Input in Junos OS - CVE-2026-21917
Published: January 20, 2026
Vulnerability identifier: #VU121698
CSH Severity: Medium
CVSS v4: 8.7 [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]
CVE-ID: CVE-2026-21917
CWE-ID: CWE-1286
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to improper validation of syntactic correctness of input error in the Web-Filtering module. A remote non-authenticated attacker can cause a Denial-of-Service (DoS) If an SRX device configured for UTM Web-Filtering receives a specifically malformed SSL packet, this will cause an FPC crash and restart.
Affected software
Junos OS
How to mitigate CVE-2026-21917
Install updates from vendor's website.
Junos OS - addressed in versions 23.2R2-S5, 23.4R2-S5, 24.2R2-S2, 24.4R1-S3, 24.4R2, 25.2R1