CVE-2026-21917: Juniper Junos

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

An Improper Validation of Syntactic Correctness of Input vulnerability in the Web-Filtering 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 device configured for UTM Web-Filtering receives a specifically malformed SSL packet, this will cause an FPC crash and restart. This issue affects Junos OS on SRX Series: * 23.2 versions from 23.2R2-S2 before 23.2R2-S5,  * 23.4 versions from 23.4R2-S1 before 23.4R2-S5, * 24.2 versions before 24.2R2-S2, * 24.4 versions before 24.4R1-S3, 24.4R2. Earlier versions of Junos are also affected, but no fix is available.

Affected products

• Juniper Junos: version 23.2 only; version 23.4 only; version 24.2 only; version 24.4 only

Published 2026-01-15. Last modified 2026-06-17.