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Stormshield Network SecurityApplication · Stormshield

CVE-2021-28096

MEDIUM · 5.3 CVSS v3.1 Published 2022-01-27
Fix available
A fix is available. Upgrade to 4.2.3 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable 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 issue was discovered in Stormshield SNS before 4.2.3 (when the proxy is used). An attacker can saturate the proxy connection table. This would result in the proxy denying any new connections.

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 · moderate confidence

This is a resource exhaustion denial-of-service vulnerability in Stormshield SNS proxy. An attacker can flood the proxy with connections, saturating the connection table and preventing legitimate new connections from being established.

MitigationUpgrade to Stormshield SNS version 4.2.3 or later. Consider implementing connection rate limiting or temporary network-level filtering if immediate upgrade is not feasible.

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
Stormshield Network SecurityApplication
Affected:>= 2.0.0, <= 2.7.8>= 3.7.6, <= 3.7.20>= 3.8.0, <= 3.11.8>= 4.0.1, < 4.2.3

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 checks

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

  1. Confirm Stormshield SNS is installed
    Identify if the target system is running Stormshield Network Security (SNS) - typically accessible via the admin web interface or CLI with command 'cli -c "show system"' or similar system information command
    Affected if The system is not running Stormshield SNS product
  2. Determine installed SNS version
    Retrieve the installed version via CLI command (such as 'cli -c "show version"' or through the web administration interface under System > Maintenance or About section)
    Affected if The installed version falls within any of these ranges: 2.0.0 to 2.7.8, 3.7.6 to 3.7.20, 3.8.0 to 3.11.8, or 4.0.1 to 4.2.2
  3. Verify proxy service is enabled
    Check if the SNS proxy functionality is active - typically via CLI command like 'cli -c "show proxy config"' or through the web interface under Proxy > Configuration
    Affected if The proxy service is enabled and running on the SNS device
  4. Inspect connection table saturation
    Review current connection/session count in the proxy - typically via CLI command such as 'cli -c "show connection table"' or 'cli -c "show proxy statistics"' to observe connection count and limits
    Affected if Connection table shows high utilization approaching limits, indicating potential exploitation in progress

A system is affected if it runs Stormshield SNS version 2.0.0-2.7.8, 3.7.6-3.7.20, 3.8.0-3.11.8, or 4.0.1-4.2.2 with the proxy feature enabled, allowing connection exhaustion attacks.

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
Upgrade available Upgrade to 4.2.3 or later
Fixed in 4.2.3
Interim mitigation

Upgrade to Stormshield SNS version 4.2.3 or later. Consider implementing connection rate limiting or temporary network-level filtering if immediate upgrade is not feasible.

Recommended fix Moderate confidence

4.2.3 or later

  1. Verify current SNS version via the administration interface or CLI command (CLI: 'fwadmin -v' or through the web UI under Status > System)
  2. Review current configuration and back up the configuration file (Configuration > Backup/Restore)
  3. Download SNS version 4.2.3 or later from the Stormshield customer portal (support.stormshield.eu)
  4. Upload the upgrade file through the administration interface (Configuration > Update > Upload) or via CLI
  5. Reboot the appliance after the upgrade completes
  6. Verify the proxy service is functioning and new connections can be established
  7. Confirm the version is 4.2.3 or later
Caveat Review Stormshield release notes for 4.2.x series before upgrading; major version upgrades may require configuration adjustments

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

Fix this in Stormshield Network Security Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,480
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Scan for this in your stack

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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-2021-28096 in production — separate from our analysis above.

No notes yet

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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