CVE-2026-33803
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 · uneditedAn Improper Restriction of Communication Channel to Intended Endpoints vulnerability in Juniper Networks Junos OS Evolved allows an unauthenticated, network-based attacker to cause a limited information disclosure and availability impact to the device. Due to a wrong initialization, a process which should only be able to communicate internally within the device can be reached over the network via an open port. This leads to a device being inadvertently exposed and increased CPU cycles spent processing ingress packets. This issue affects Junos OS Evolved: * all versions before 23.2R2-S7-EVO, * 23.4 versions before 23.4R2-S8-EVO, * 24.2 versions before 24.2R2-S5-EVO, * 24.4 versions before 24.4R2-S4-EVO, * 25.2 versions before 25.2R2-S1-EVO, * 25.4 versions before 25.4R1-S2-EVO.
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 confidenceA Juniper Junos OS Evolved internal process that should only communicate via internal device mechanisms is incorrectly initialized with network accessibility, exposing an open port to the network. This allows unauthenticated attackers to send packets to this internal process, causing limited information disclosure and increased CPU usage from processing unexpected ingress traffic.
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< 23.2= 23.2= 23.4= 24.2= 24.4= 25.2= 25.4CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
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 checksWork through these to decide whether this CVE applies to you.
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Identify the installed Junos OS Evolved versionRun 'show version' or 'request system version' to obtain the exact Junos OS Evolved version running on the deviceAffected if The installed version matches one of the affected versions: < 23.2, 23.2, 23.4, 24.2, 24.4, 25.2, or 25.4
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Identify all listening network portsUse 'show system connections' or 'netstat -an' to list all TCP and UDP ports in LISTEN state on the deviceAffected if An unexpected or undocumented port is found listening, particularly on external or non-loopback interfaces, which could indicate the misconfigured internal process
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Verify which processes are bound to listening portsRun 'show system processes' or use 'lsof -i' (if available) to identify which process owns each listening portAffected if An internal or management-only process is found bound to a network-accessible interface (0.0.0.0 or external IP) rather than localhost or internal mechanisms
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Check for unexplained CPU utilization spikesUse 'show system processes summary' or 'show chassis firmware' to monitor CPU usage, looking for processes consuming unexpectedly high resourcesAffected if A process that should only run internally is consuming elevated CPU due to processing unexpected ingress network traffic
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Review network interface bindings for internal servicesCheck the configuration or running state of internal services to confirm whether they are bound to internal-only interfaces (127.0.0.1 or internal VLANs)Affected if An internal service is bound to a globally reachable address when it should only be accessible via internal device mechanisms
If the device runs an affected Junos OS Evolved version and has an internal process unexpectedly listening on a network-accessible port, the device is affected by this CVE.
Generated from the published advisory. Verify against your own configuration.
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 · scoped23.2
Upgrade Junos OS Evolved to the patched versions specified in the advisory. If immediate patching is not possible, network filtering controls should be implemented to restrict unauthorized access to the exposed port.
23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R2-S5-EVO, 24.4R2-S4-EVO, 25.2R2-S1-EVO, or 25.4R1-S2-EVO (depending on release train)
- 1. Identify the current Junos OS Evolved version running on the device using 'show version' command
- 2. Determine which release train your current version belongs to (23.2, 23.4, 24.2, 24.4, 25.2, or 25.4)
- 3. Plan the upgrade based on your current version and select the appropriate fixed release: for 23.2 train upgrade to 23.2R2-S7-EVO or later, for 23.4 train upgrade to 23.4R2-S8-EVO or later, for 24.2 train upgrade to 24.2R2-S5-EVO or later, for 24.4 train upgrade to 24.4R2-S4-EVO or later, for 25.2 train upgrade to 25.2R2-S1-EVO or later, for 25.4 train upgrade to 25.4R1-S2-EVO or later
- 4. Download the recommended fixed Junos OS Evolved image from the Juniper support portal
- 5. Back up the current device configuration
- 6. Upload the new Junos OS Evolved image to the device
- 7. Perform a software installation using 'request system software add <package-name>' command
- 8. Reboot the device using 'request system reboot' command
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33803 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33803 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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