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Cbs250 8t D FirmwareOperating system · Cisco

CVE-2024-20263

HIGH · 7.2 CVSS v3.1 Published 2024-01-26
Fix available
A fix is available. Upgrade to 2.5.9.54 / 3.4.0.17 or later.
See remediation →
81/100
Remediation priority · High
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
A vulnerability with the access control list (ACL) management within a stacked switch configuration of Cisco Business 250 Series Smart Switches and Business 350 Series Managed Switches could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device. This vulnerability is due to incorrect processing of ACLs on a stacked configuration when either the primary or backup switches experience a full stack reload or power cycle. An attacker could exploit this vulnerability by sending crafted traffic through an affected device. A successful exploit could allow the attacker to bypass configured ACLs, causing traffic to be dropped or forwarded in an unexpected manner. The attacker does not have control over the conditions that result in the device being in the vulnerable state. Note: In the vulnerable state, the ACL would be correctly applied on the primary devices but could be incorrectly applied to the backup devices.

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

A logic flaw in Cisco Business 250/350 Series Switches causes incorrect ACL processing on backup switches after a full stack reload or power cycle. While ACLs remain correctly applied on the primary device, the backup devices fail to apply ACLs properly, allowing an unauthenticated remote attacker to bypass configured ACLs and cause unexpected traffic forwarding or dropping.

MitigationApply the Cisco firmware update for this vulnerability; if no update is available, monitor for reload/power cycle events and manually verify ACL enforcement across all stack members until a patch is deployed.

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
Cbs250 8t D FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 8pp D FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 8t E 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 8pp E 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 8p E 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 8fp E 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54
Cbs250 16t 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, <= 2.5.9.54
Cbs250 16p 2g FirmwareOperating system
Affected:>= 3.4, < 3.4.0.17>= 2.5, < 2.5.9.54

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
Changed
Confidentiality
None
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/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. Identify the device model
    Run 'show version' or physically inspect the device label to confirm it is a Cisco Business 250 Series switch (CBS250) such as CBS250-8T-D, CBS250-8PP-D, CBS250-8T-E-2G, CBS250-8PP-E-2G, CBS250-8P-E-2G, CBS250-8FP-E-2G, CBS250-16T-2G, or CBS250-16P-2G
    Affected if Device is not one of the listed CBS250 models - not affected by this CVE
  2. Check the firmware version
    Run 'show version' to display the current firmware version. Compare against the affected version ranges: 3.4.x versions prior to 3.4.0.17, and 2.5.x versions prior to 2.5.9.54 (or <= 2.5.9.54 for CBS250-16T-2G model)
    Affected if Firmware version is >= 3.4.0.0 and < 3.4.0.17, OR >= 2.5.0.0 and < 2.5.9.54 (or <= 2.5.9.54 for CBS250-16T-2G)
  3. Verify ACLs are configured
    Run 'show access-lists' or 'show ip access-lists' to list any configured access control lists on the device
    Affected if No ACLs are configured - the bypass cannot occur as there are no ACLs to bypass on the backup switch
  4. Confirm stack or redundancy configuration
    Run 'show stack' or 'show switch' to verify if the device is part of a stack configuration with multiple switches
    Affected if Device is part of a stack with backup members - the vulnerability specifically affects backup switches after a full stack reload or power cycle

Device is affected if it is a CBS250 model running firmware version 3.4.x before 3.4.0.17 or 2.5.x before 2.5.9.54, has ACLs configured, and is part of a stack where backup switches can fail to apply ACLs after reload or power cycle.

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 2.5.9.54 / 3.4.0.17 or later
Fixed in 2.5.9.543.4.0.17
Interim mitigation

Apply the Cisco firmware update for this vulnerability; if no update is available, monitor for reload/power cycle events and manually verify ACL enforcement across all stack members until a patch is deployed.

Recommended fix High confidence

Upgrade to firmware 3.4.0.17 or later, or 2.5.9.54 or later (prefer latest available in respective branch)

  1. Identify the current firmware version of the CBS250 switch by accessing the web interface or CLI
  2. Determine which firmware branch (2.5.x or 3.4.x) is currently in use
  3. Download the fixed firmware version from Cisco's official support website (sec.cloudapps.cisco.com or cisco.com)
  4. Verify the firmware file matches the specific switch model number
  5. Upload the firmware through the switch's web interface or CLI following Cisco's standard upgrade procedure
  6. After upgrade, verify the ACL functionality works correctly, especially in stacked configurations
  7. Confirm the new firmware version is >= 3.4.0.17 or >= 2.5.9.54
Caveat Firmware upgrades carry inherent risks; backup configuration before upgrading; test in lab environment first if possible

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

Fix this in Cbs250 8t D Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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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-2024-20263 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