CVE-2025-21591

Junos OS: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhcpd to crash

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.

Remediation

Solution:

  • The following software releases have been updated to resolve this specific issue: 23.2R2-S3, 23.4R2-S3, 24.2R2, 24.4R1, and all subsequent releases.

Workaround:

  • There are no known workarounds for this issue.

Category

7.1
CVSS
Severity: High
CVSS 4.0 •
CVSS 3.1 •
EPSS 0.02%
Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Published at:
Updated at:

References

Frequently Asked Questions

What is the severity of CVE-2025-21591?
CVE-2025-21591 has been scored as a high severity vulnerability.
How to fix CVE-2025-21591?
To fix CVE-2025-21591: The following software releases have been updated to resolve this specific issue: 23.2R2-S3, 23.4R2-S3, 24.2R2, 24.4R1, and all subsequent releases.
Is CVE-2025-21591 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2025-21591 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-21591?
CVE-2025-21591 affects Juniper Networks Junos OS.
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