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JunosOperating system · Juniper

CVE-2026-33797

HIGH · 7.4 CVSS v3.1 Published 2026-04-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
79/100
Remediation priority · High
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 does not affect Junos OS versions before 25.2R1. This issue affects Junos OS Evolved: * 25.2-EVO versions before 25.2R2-EVO This issue does not affect Junos OS Evolved versions before 25.2R1-EVO. eBGP and iBGP are affected. IPv4 and IPv6 are affected.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

An improper input validation vulnerability in Juniper Junos OS and Junos OS Evolved allows an unauthenticated, adjacent attacker to send a specific genuine BGP packet within an established BGP session to reset only that session, causing a denial of service. Repeated packets can sustain the DoS. Both eBGP and iBGP are affected across IPv4 and IPv6.

MitigationUpgrade to Junos OS 25.2R2 or later / Junos OS Evolved 25.2R2-EVO or later to remediate this vulnerability. If immediate patching is not possible, consider implementing BGP route filtering or authentication to reduce the attack surface.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JunosOperating system
Affected:= 25.2
Junos Os EvolvedOperating system
Affected:= 25.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Junos OS version
    Run the command 'show version' or 'show version detail' on the device to obtain the exact software version
    Affected if The version displayed is exactly 25.2 (any subversion like 25.2-S1, 25.2-R1, etc.) rather than 25.2R2 or later
  2. Confirm BGP protocol is configured
    Run 'show configuration protocols bgp' or 'show bgp summary' to see if BGP is enabled and has configured peers
    Affected if BGP is actively configured with one or more peers
  3. Verify active BGP sessions exist
    Run 'show bgp neighbor' or 'show bgp summary' to list established BGP sessions
    Affected if There are active eBGP or iBGP sessions over IPv4 or IPv6
  4. Assess network exposure to adjacent attackers
    Review the BGP peer configurations (peer addresses, interface attachments) to determine if peers are reachable from untrusted adjacent network segments
    Affected if BGP peers are accessible from network segments where unauthenticated adjacent attackers could send packets (e.g., directly connected networks, layer 2 adjacencies)

You are affected if your Junos/Junos OS Evolved version is exactly 25.2, BGP is configured with active sessions, and those sessions are reachable by unauthenticated adjacent attackers on the local network segment.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Junos OS 25.2R2 or later / Junos OS Evolved 25.2R2-EVO or later to remediate this vulnerability. If immediate patching is not possible, consider implementing BGP route filtering or authentication to reduce the attack surface.

Recommended fix High confidence

Junos OS 25.2R2 or later; Junos OS Evolved 25.2R2-EVO or later

  1. 1. Identify the current Junos OS or Junos OS Evolved version running on the affected device using 'show version' command.
  2. 2. Confirm the device is running a vulnerable version (25.2, 25.2R1, or any 25.2x version before 25.2R2 for Junos OS; or 25.2R1-EVO or any 25.2-EVO version before 25.2R2-EVO).
  3. 3. Schedule a maintenance window for the upgrade, as BGP session disruption will occur during the upgrade process.
  4. 4. Download the fixed software image (25.2R2 or later for Junos OS; 25.2R2-EVO or later for Junos OS Evolved) from the Juniper Networks support portal.
  5. 5. Upload the new software image to the device using 'request system software add' command.
  6. 6. Reboot the device using 'request system reboot' command to apply the new software.
  7. 7. After the device restarts, verify the new version is running with 'show version' and confirm BGP sessions are re-established.
  8. 8. Verify the fix is applied by checking that the specific malicious BGP packet no longer causes session reset.
Caveat Upgrading may cause brief BGP session disruption; ensure proper change control and maintenance window are followed

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33797 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data