Junos OS (SRX firewalls)
CVE-2026-101987: A specific IS-IS SRv6 packet causes an rpd crash when flexible algorithm is used
An Improper Validation of Specified Quantity in Input vulnerability in the routing daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent attacker to cause a denial of service by sending a specific IS-IS SRv6 packet when SRv6 and Flexible Algorithm are enabled.
Published Juniper Networks advisory JSA112187
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| Junos OS 0 | 23.2R2-S7.7 or later |
| Junos OS 23.4 | 23.4R2-S8.13 or later |
| Junos OS 24.2 | 24.2R2-S5.5 or later |
| Junos OS 24.4 | 24.4R2-S5 or later |
| Junos OS 25.2 | 25.2R2-S2 or later |
| Junos OS 25.4 | 25.4R1-S3 or later |
| Junos OS 26.2 | 26.2R1-S2 or later |
| Junos OS Evolved 0 | 23.2R2-S7.7-EVO or later |
| Junos OS Evolved 23.4 | 23.4R2-S8.11-EVO or later |
| Junos OS Evolved 24.2 | 24.2R2-S5.6-EVO or later |
| Junos OS Evolved 24.4 | 24.4R2-S5-EVO or later |
| Junos OS Evolved 25.2 | 25.2R2-S2-EVO or later |
| Junos OS Evolved 25.4 | 25.4R1-S3-EVO or later |
| Junos OS Evolved 26.2 | 26.2R1-S2-EVO or later |
| Junos OS Evolved 23.4X100 | See the advisory |
| Junos OS Evolved 25.2X100 | 25.2X100-D35-EVO or later |
| Junos OS Evolved 25.4X300 | 25.4X300-D40-EVO or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
In short
An improper input validation flaw in the routing daemon of Junos OS allows an attacker on an adjacent network to trigger a denial of service. By sending a specific IS-IS SRv6 packet, the attacker can disrupt service without needing to log in or interact with users. This vulnerability is only exploitable when SRv6 and Flexible Algorithm features are enabled on the device.
Written by a language model from the vendor's description. Versions, fixes and exploitation status on this page come straight from the vendor and CISA.
The vendor's description
An Improper Validation of Specified Quantity in Input vulnerability in the routing daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent attacker to cause a denial of service by sending a specific IS-IS SRv6 packet when SRv6 and Flexible Algorithm are enabled.
Am I affected?
[ protocols isis source-packet-routing srv6 ] [ routing-options flex-algorithm ]
Workarounds
There are no known workarounds for this issue.
Exploitation
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 19 Oct 2026.