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Vulnerabilities

Vulnerability · CVE-2026-33781

An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX and QFX Series…

Published Apr 9, 2026 · catalog updated Jun 17, 2026 · the affected product

Check if you run it

No confirmed exploitation is on record for CVE-2026-33781. EPSS is 0.27%. Act only if a listed version of the affected product is installed.

Gaps on this record

  • No plain product name is stored. The page cannot tell you which product to check.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.27%
Remediation
Not established
Affected products
cpe juniper/junos

An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX and QFX Series devices allow an unauthenticated, adjacent attacker to cause a complete Denial of Service (DoS). On EX4k, and QFX5k platforms configured as service-provider edge devices, if L2PT is enabled on the UNI and VSTP is enabled on NNI in VXLAN scenarios, receiving VSTP BPDUs on UNI leads to packet buffer allocation failures, resulting in the device to not pass traffic anymore until it is manually recovered with a restart.This issue affects Junos OS: * 24.4 releases before 24.4R2, * 25.2 releases before 25.2R1-S1, 25.2R2. This issue does not affect Junos OS releases before 24.4R1.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe juniper/junos24.4
  • cpe juniper/junos25.2

How to fix CVE-2026-33781

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33781. EPSS is 0.27%. Act only if a listed version of the affected product is installed.

Which versions are affected?

Compare what you have installed with 24.4, 25.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-754. EPSS 0.27%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 9, 2026 · NIST NVD

    Detected

    An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX and QFX Series devices allow an unauthenticated, adjacent attacker to cause a complete Denial of Service (DoS). On EX4k, and QFX5k platforms configured as service-provider edge devices, if L2PT is enabled on the UNI and VSTP is enabled on NNI in VX

  2. Jun 17, 2026 · NIST NVD

    Updated

    An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX and QFX Series devices allow an unauthenticated, adjacent attacker to cause a complete Denial of Service (DoS). On EX4k, and QFX5k platforms configured as service-provider edge devices, if L2PT is enabled on the UNI and VSTP is enabled on NNI in VX

Sources

  • CVE.orgVulnerability recordCVE-2026-33781

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33781

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33781

    An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on specific EX and QFX Series devices allow an unauthenticated, adjacent attacker to cause a complete Denial of Service (DoS). On EX4k, and QF

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.