Sf250 24 FirmwareOperating system · Cisco
CVE-2021-34739
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 · uneditedA vulnerability in the web-based management interface of multiple Cisco Small Business Series Switches could allow an unauthenticated, remote attacker to replay valid user session credentials and gain unauthorized access to the web-based management interface of an affected device. This vulnerability is due to insufficient expiration of session credentials. An attacker could exploit this vulnerability by conducting a man-in-the-middle attack against an affected device to intercept valid session credentials and then replaying the intercepted credentials toward the same device at a later time. A successful exploit could allow the attacker to access the web-based management interface with administrator privileges.
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 confidenceSession replay vulnerability in Cisco Small Business Series Switches web-based management interface. Insufficient expiration of session credentials allows an attacker conducting a man-in-the-middle attack to intercept valid session tokens and replay them at a later time to gain unauthorized administrative access to the device management interface.
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
Sf250 24 FirmwareOperating system
<= 2.5
Sf250 24p FirmwareOperating system
<= 2.5
Sf250 48 FirmwareOperating system
<= 2.5
Sf250 48hp FirmwareOperating system
<= 2.5
Sf250 08 FirmwareOperating system
<= 2.5
Sf250 08hp FirmwareOperating system
<= 2.5
Sf250 10p FirmwareOperating system
<= 2.5
Sf250 18 FirmwareOperating system
<= 2.5CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify the switch modelLog into the switch CLI or check the web interface to confirm the exact model number (e.g., Sf250-24, Sf250-48, etc.)Affected if The model is any of the following: Sf250 24, Sf250 24p, Sf250 48, Sf250 48hp, Sf250 08, Sf250 08hp, Sf250 10p, or Sf250 18
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Check the installed firmware versionAccess the switch web-based management interface and navigate to the Administration > Firmware Upgrade or Status page, or use the CLI command 'show version' to retrieve the firmware versionAffected if The firmware version is 2.5 or any earlier version (e.g., 2.4.x, 2.3.x, etc.)
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Verify web-based management interface is enabledCheck the switch configuration via CLI with 'show running-config | include http' or through the web interface under Administration > Management Interface > HTTP/HTTPS settingsAffected if HTTP or HTTPS web management is enabled (the vulnerability applies to the web-based management interface)
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Check if the management interface is exposed to untrusted networksReview the switch network configuration to determine if the management interface (HTTP/HTTPS) is bound to a VLAN accessible from outside the trusted internal network, or check ACLs and firewall rules protecting the management IPAffected if The web management interface is accessible from networks beyond the trusted internal network (the attack requires a man-in-the-middle position on the network path to the management interface)
You are affected if you have one of the listed Sf250 models running firmware version 2.5 or lower and the web-based management interface is enabled and accessible.
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.
From vendor dataApply Cisco firmware updates for affected Small Business Switch models. In the interim, minimize exposure by restricting management interface access to trusted networks, using VPN access, and ensuring HTTPS is enforced for all management sessions.
Fix this in Sf250 24 Firmware
Scoped from the published advisory
- Consultation6.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,448.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34739 — 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-2021-34739 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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- 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
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