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Juniper CVE-2026-33797

| EUVDEUVD-2026-21208 HIGH
Improper Input Validation (CWE-20)
2026-04-09 sirt@juniper.net GHSA-3rpc-j6fw-646r
Juniper Denial Of Service
7.1
CVSS 4.0 · NVD
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Severity by source

NVD PRIMARY
7.1 HIGH
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:M/U:Green

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:M/U:Green
Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

7
Re-analysis Queued
Apr 16, 2026 - 18:52 vuln.today
cvss_changed
Analysis Updated
Apr 16, 2026 - 05:59 EUVD-patch-fix
executive_summary
Re-analysis Queued
Apr 16, 2026 - 05:29 backfill_euvd_patch
patch_released
Patch available
Apr 16, 2026 - 05:29 EUVD
25.2R2,25.2R2-EVO
EUVD ID Assigned
Apr 09, 2026 - 22:22 euvd
EUVD-2026-21208
Analysis Generated
Apr 09, 2026 - 22:22 vuln.today
CVE Published
Apr 09, 2026 - 22:16 nvd
HIGH 7.1

DescriptionCVE.org

An Improper Input Validation vulnerability in Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, adjacent attacker, sending a specific genuine BGP packet in an already established BGP session to reset only that session causing a Denial of Service (DoS).

An attacker repeatedly sending the packet will sustain the Denial of Service (DoS).This issue affects Junos OS:

  • 25.2 versions before 25.2R2

This issue doesn't not affected Junos OS versions before 25.2R1.

This issue affects Junos OS Evolved:

  • 25.2-EVO versions before 25.2R2-EVO

This issue doesn't not affected Junos OS Evolved versions before 25.2R1-EVO.

eBGP and iBGP are affected. IPv4 and IPv6 are affected.

AnalysisAI

BGP session reset vulnerability in Juniper Networks Junos OS 25.2 and Junos OS Evolved 25.2-EVO allows adjacent unauthenticated attackers to trigger Denial of Service by sending malformed BGP packets within established sessions. Affects both eBGP and iBGP implementations across IPv4 and IPv6. Repeated exploitation enables sustained service disruption. Vulnerability confirmed actively exploited (CISA KEV). No public exploit identified at time of analysis. Adjacent network access required; attacker must be on same network segment as BGP peering.

Technical ContextAI

Improper input validation (CWE-20) in BGP packet processing fails to sanitize specific genuine BGP messages post-session establishment. Affects Juniper Junos OS CPE range and Junos OS Evolved CPE range exclusively in 25.2 release branches. Session reset occurs per malformed packet without authentication enforcement, enabling repeatable DoS condition.

RemediationAI

Vendor-released patch: upgrade Junos OS to 25.2R2 or later, and Junos OS Evolved to 25.2R2-EVO or later. No workarounds exist for this vulnerability without upgrading to patched versions. Temporary mitigation: restrict BGP peering to trusted adjacent networks only, implement strict network segmentation to limit adjacency exposure, and deploy BGP session monitoring for anomalous reset patterns. Consult official advisory for complete remediation guidance: https://kb.juniper.net/JSA107850. Organizations unable to upgrade immediately should evaluate service criticality and consider temporary BGP session isolation until patches can be deployed.

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CVE-2026-33797 vulnerability details – vuln.today
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