CVE-2026-33781

Traffic halt via VSTP packet buffer exhaustion

Published Apr 9, 2026 · Updated Apr 9, 2026

Denial of service in Junos OS allows attackers on an adjacent network to halt traffic by sending VSTP BPDUs in configured VXLAN deployments. The packet forwarding engine fails to handle those control frames without exhausting packet-buffer allocations. Reachability requires an EX4k or QFX5k service-provider edge configuration with L2PT on the UNI and VSTP on the NNI; traffic remains stopped until a manual restart.

CVSS severity7.1
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Junos OS allows attackers on an adjacent network to halt traffic by sending VSTP BPDUs in configured VXLAN deployments. The packet forwarding engine fails to handle those control frames without exhausting packet-buffer allocations. Reachability requires an EX4k or QFX5k service-provider edge configuration with L2PT on the UNI and VSTP on the NNI; traffic remains stopped until a manual restart.

The record

CVE
CVE-2026-33781
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-754, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 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=24.4 <24.4R2
  2. Affected versionversion=25.2 <25.2R1-S1, 25.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=24.4 <24.4R2; version=25.2 <25.2R1-S1, 25.2R2

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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
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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