CVE-2025-21591 Junos OS: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhcpd to crash
An unauthenticated adjacent attacker can crash the jdhcpd daemon by sending malformed DHCP packets when DHCP snooping is enabled, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-21591?
CVE-2025-21591 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Weakness: CWE-805
Which versions are affected by CVE-2025-21591?
It affects 1 product.
Products include Juniper Junos.
How do I fix CVE-2025-21591?
No fix has been published for CVE-2025-21591 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-21591 being exploited?
There is no known exploitation of CVE-2025-21591 in the wild and no public exploit code.
Other vulnerabilities in Juniper Junos
- CVE-2023-36845 Juniper Junos OS EX Series and SRX Series PHP External Variable Modification
- CVE-2020-1631 Juniper Junos OS Path Traversal
- CVE-2025-21590 Juniper Junos OS Improper Isolation or Compartmentalization
- CVE-2023-36851 Juniper Junos OS SRX Series Missing Authentication for Critical Function
- CVE-2023-36844 Juniper Junos OS EX Series PHP External Variable Modification
Sources
Also known as GHSA-6pgh-5wh4-5pph.