CVE-2026-57027

FPC restart via multicast sFlow memory leak

Published Jul 9, 2026 · Updated Jul 9, 2026

Memory exhaustion in Junos OS on EX4100 and EX4400 devices allows attackers on an adjacent network to crash and restart an FPC. The packet forwarding engine fails to release buffers while multicast traffic crosses between Virtual Chassis members under egress multicast sFlow sampling. No authentication is required, but only Virtual Chassis deployments with forwarding-options sflow egress-multicast enable explicitly configured are affected; sustained traffic exhausts memory until the FPC restarts.

CVSS severity6.5
Medium
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

Memory exhaustion in Junos OS on EX4100 and EX4400 devices allows attackers on an adjacent network to crash and restart an FPC. The packet forwarding engine fails to release buffers while multicast traffic crosses between Virtual Chassis members under egress multicast sFlow sampling. No authentication is required, but only Virtual Chassis deployments with forwarding-options sflow egress-multicast enable explicitly configured are affected; sustained traffic exhausts memory until the FPC restarts.

The record

CVE
CVE-2026-57027
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-401, 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-S7
  3. Affected versionversion=24.2 <24.2R2-S4
  4. Affected versionversion=24.4 <24.4R2

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-S7; version=24.2 <24.2R2-S4; version=24.4 <24.4R2

Published CVSS scores

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
6.5Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-401Missing Release of Memory after Effective Lifetime
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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