CVE-2025-21591

Adjacent service interruption via malformed DHCP option

Published Apr 9, 2025 · Updated Apr 28, 2025

Buffer access with an incorrect length in Juniper Networks Junos OS allows attackers to crash jdhcpd using a malformed DHCP option. The daemon uses an incorrect length while accessing a buffer during DHCP-option processing, allowing out-of-bounds memory access; Juniper has not named the routine. The target must have DHCP snooping enabled and the attacker must share an adjacent network; repeated packets sustain the service interruption.

CVSS severity7.1
High
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer access with an incorrect length in Juniper Networks Junos OS allows attackers to crash jdhcpd using a malformed DHCP option. The daemon uses an incorrect length while accessing a buffer during DHCP-option processing, allowing out-of-bounds memory access; Juniper has not named the routine. The target must have DHCP snooping enabled and the attacker must share an adjacent network; repeated packets sustain the service interruption.

The record

CVE
CVE-2025-21591
Published
Apr 9, 2025
Updated
Apr 28, 2025
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-805, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=23.1 <23.2R2-S3
  2. Affected versionversion=23.4 <23.4R2-S3
  3. Affected versionversion=24.2 <24.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=23.1 <23.2R2-S3; version=23.4 <23.4R2-S3; version=24.2 <24.2R2

Published CVSS scores

7.4Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.1Juniper NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/V:C/RE:M/U:Green

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-805Buffer Access with Incorrect Length Value
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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