CVE-2026-33800

FPC crash via unbounded PFEMAN event queue

Published Jul 9, 2026 · Updated Jul 9, 2026

Unchecked loop input in Junos OS on affected MX Series FPCs allows attackers to crash and restart an FPC through micro-BFD flapping. PFEMAN queues every up/down event but cannot drain the queue when sustained flapping makes per-event processing too slow, so its watchdog expires. Reachability is adjacent and is most pronounced in a Virtual Chassis with locality-bias configured; the restart causes a complete service outage.

CVSS severity7.1
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unchecked loop input in Junos OS on affected MX Series FPCs allows attackers to crash and restart an FPC through micro-BFD flapping. PFEMAN queues every up/down event but cannot drain the queue when sustained flapping makes per-event processing too slow, so its watchdog expires. Reachability is adjacent and is most pronounced in a Virtual Chassis with locality-bias configured; the restart causes a complete service outage.

The record

CVE
CVE-2026-33800
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-606, T1499.002
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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=0 <23.2R2-S7
  2. Affected versionversion=23.4 <23.4R2-S8
  3. Affected versionversion=24.2 <24.2R2-S4
  4. Affected versionversion=24.4 <24.4R2-S3
  5. Affected versionversion=25.2 <25.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=0 <23.2R2-S7; version=23.4 <23.4R2-S8; version=24.2 <24.2R2-S4; version=24.4 <24.4R2-S3; version=25.2 <25.2R2

Published CVSS scores

6.5Juniper Networks, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.1Juniper Networks, Inc.CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L

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.

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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-606Unchecked Input for Loop Condition
T1499.002Service Exhaustion

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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