Junos OS (SRX firewalls)
CVE-2025-21591: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhcpd to crash
A Buffer Access with Incorrect Length Value vulnerability in the jdhcpd daemon of Juniper Networks Junos OS, when DHCP snooping is enabled, allows an unauthenticated, adjacent, attacker to send a DHCP packet with a malformed DHCP option to cause jdhcp to crash creating a Denial of Service (DoS) condition.
Published
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 23.1 | 23.2R2-S3 or later |
| Junos OS 23.4 | 23.4R2-S3 or later |
| Junos OS 24.2 | 24.2R2 or later |
| Junos OS 0 | Not affected |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
A Buffer Access with Incorrect Length Value vulnerability in the jdhcpd daemon of Juniper Networks Junos OS, when DHCP snooping is enabled, allows an unauthenticated, adjacent, attacker to send a DHCP packet with a malformed DHCP option to cause jdhcp to crash creating a Denial of Service (DoS) condition.
Continuous receipt of these DHCP packets using the malformed DHCP Option will create a sustained Denial of Service (DoS) condition.
This issue affects Junos OS:
- from 23.1 before 23.2R2-S3,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
This issue isn't applicable to any versions of Junos OS before 23.1R1.
This issue doesn't affect vSRX Series which doesn't support DHCP Snooping.
This issue doesn't affect Junos OS Evolved.
There are no indicators of compromise for this issue.
Am I affected?
The required minimal configuration is DHCP is configured with DHCP snooping enabled with the mine-dhcp-client-options and/or mine-dhcpv6-client-options. [ vlans <vlan-name> forwarding-options dhcp-security mine-dhcp-client-options ] [ mine-dhcpv6-client-options ]
Please note: It is atypical to use the above configuration with a DHCP server on the same device.
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 13 Oct 2026.