CVE-2026-33800
Full vulnerability record from the local CVENow database.
Description
An Unchecked Input for Loop Condition vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage. This issue only affects MX series FPCs up to and including MPC9, and LC2101/2103 and LC480. It does not affect MPC10/11, LC4800/9600, and MX304. This issue affects Junos OS on MX Series: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R2.
Severity
HIGH
CVSS score
7.1
(v4.0)
Vulnerability status
Analyzed
Source identifier
Published
2026-07-09 21:16:55.163000
Last modified
2026-10-25 17:10:00.197000
View original CVE JSON
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"sourceIdentifier": "[email protected]",
"published": "2026-07-09T21:16:55.163",
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"value": "An Unchecked Input for Loop Condition vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage.\n\n\nThis issue only affects MX series FPCs up to and including MPC9, and LC2101/2103 and LC480. It does not affect MPC10/11, LC4800/9600, and MX304.\n\nThis issue affects Junos OS on MX Series:\n\n\n * all versions before 23.2R2-S7,\n * 23.4 versions before 23.4R2-S8,\n * 24.2 versions before 24.2R2-S4,\n * 24.4 versions before 24.4R2-S3,\n * 25.2 versions before 25.2R2."
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"value": "Una vulnerabilidad de Condición de Bucle con Entrada No Verificada en el Motor de Reenvío de Paquetes (pfe) de Juniper Networks Junos OS en la Serie MX permite a un atacante adyacente no autenticado causar una Denegación de Servicio (DoS). Las fluctuaciones de sesión de Micro-BFD generan eventos de subida/bajada respectivos que son encolados por PFEMAN para su procesamiento. Especialmente en un escenario de Chasis Virtual (VC) con sesgo de localidad configurado, el procesamiento lleva una cantidad significativa de tiempo para cada evento. Si estas sesiones siguen fluctuando, se añaden constantemente nuevos eventos, y a su vez PFEMAN nunca completa el procesamiento de estos eventos. Esto resulta en la expiración del temporizador de vigilancia de PFEMAN, lo que provoca que la FPC se bloquee y reinicie, lo que representa una interrupción completa del servicio.\n\nEste problema solo afecta a las FPC de la serie MX hasta e incluyendo MPC9. No afecta a MPC10/11, LC4800/9600 y MX304.\n\nEste problema afecta a Junos OS en la Serie MX:\n\n * todas las versiones anteriores a 23.2R2-S7,\n * versiones 23.4 anteriores a 23.4R2-S8,\n * versiones 24.2 anteriores a 24.2R2-S4,\n * versiones 24.4 anteriores a 24.4R2-S3,\n * versiones 25.2 anteriores a 25.2R2."
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],
"references": [
{
"url": "https://supportportal.juniper.net/JSA110075",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
}
]
}