CVE-2025-59960
Published: 15 January 2026
Summary
CVE-2025-59960 is a medium-severity Improper Check for Unusual or Exceptional Conditions (CWE-754) vulnerability in Juniper Junos. Its CVSS base score is 6.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Service Exhaustion Flood (T1499.002); ranked at the 1.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and AC-4 (Information Flow Enforcement).
Deeper analysis
CVE-2025-59960 is an Improper Check for Unusual or Exceptional Conditions vulnerability (CWE-754) in the Juniper DHCP service (jdhcpd) of Juniper Networks Junos OS and Junos OS Evolved. The flaw affects numerous versions, including all Junos OS releases prior to 21.2R3-S10, versions from 21.4 prior to 21.4R3-S12, all 22.2 versions, and ranges in later branches up to 25.2R2 such as 22.4 prior to 22.4R3-S8, 23.2 prior to 23.2R2-S5, and others; similar version ranges apply to Junos OS Evolved. By default, the DHCP relay agent inserts its own Option 82 information when forwarding client requests, but in 'forward-only' mode, it fails to drop specific DHCP DISCOVER packets containing Option 82 unless 'trust-option82' is configured, instead forwarding them unmodified to the DHCP server.
An attacker with adjacent network access (AV:A) and no privileges (PR:N) can exploit this by sending crafted DHCP DISCOVER packets with Option 82 from one subnet. The relay agent forwards these unmodified to the downstream DHCP server, causing it to allocate addresses from unintended pools and exhaust those of other subnets. This results in a high-impact Denial of Service (DoS) on the DHCP server (A:H, scope changed S:C), with a CVSS v3.1 base score of 7.4.
The Juniper security advisory at https://kb.juniper.net/JSA103149 details fixed versions for mitigation, recommending upgrades to patched releases such as Junos OS 21.2R3-S10 or later in the respective branches, and equivalent Junos OS Evolved versions like 21.4R3-S12-EVO. Additional guidance is available via https://supportportal.juniper.net/.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2718
Vulnerability details
An Improper Check for Unusual or Exceptional Conditions vulnerability in the Juniper DHCP service (jdhcpd) of Juniper Networks Junos OS and Junos OS Evolved allows a DHCP client in one subnet to exhaust the address pools of other subnets, leading…
more
to a Denial of Service (DoS) on the downstream DHCP server. By default, the DHCP relay agent inserts its own Option 82 information when forwarding client requests, optionally replacing any Option 82 information provided by the client. When a specific DHCP DISCOVER is received in 'forward-only' mode with Option 82, the device should drop the message unless 'trust-option82' is configured. Instead, the DHCP relay forwards these packets to the DHCP server unmodified, which uses up addresses in the DHCP server's address pool, ultimately leading to address pool exhaustion. This issue affects Junos OS: * all versions before 21.2R3-S10, * from 21.4 before 21.4R3-S12, * all versions of 22.2, * from 22.4 before 22.4R3-S8, * from 23.2 before 23.2R2-S5, * from 23.4 before 23.4R2-S6, * from 24.2 before 24.2R2-S2, * from 24.4 before 24.4R2, * from 25.2 before 25.2R1-S1, 25.2R2. Junos OS Evolved: * all versions before 21.4R3-S12-EVO, * all versions of 22.2-EVO, * from 22.4 before 22.4R3-S8-EVO, * from 23.2 before 23.2R2-S5-EVO, * from 23.4 before 23.4R2-S6-EVO, * from 24.2 before 24.2R2-S2-EVO, * from 24.4 before 24.4R2-EVO, * from 25.2 before 25.2R1-S1-EVO, 25.2R2-EVO.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability in DHCP relay enables crafted Option 82 packets that directly cause address pool exhaustion on the server, matching Service Exhaustion Flood.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires validation of DHCP inputs to reject exceptional Option 82 data in forward-only mode before packets reach the server.
Enforces information flow policies that prevent DHCP DISCOVER messages from one subnet from improperly allocating addresses in other subnets.
Controls communications at network boundaries to block unauthorized forwarding of crafted DHCP packets by the relay agent.