CVE-2021-1339
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 · uneditedMultiple vulnerabilities in the web-based management interface of Cisco Small Business RV016, RV042, RV042G, RV082, RV320, and RV325 Routers could allow an authenticated, remote attacker to execute arbitrary code or cause an affected device to restart unexpectedly. These vulnerabilities are due to improper validation of user-supplied input in the web-based management interface. An attacker could exploit these vulnerabilities by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as the root user on the underlying operating system or cause the device to reload, resulting in a denial of service (DoS) condition. To exploit these vulnerabilities, an attacker would need to have valid administrator credentials on the affected device.
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 confidenceMultiple input validation flaws in the web-based management interface of Cisco Small Business RV series routers allow an authenticated attacker with admin credentials to send specially crafted HTTP requests that result in arbitrary code execution as root user or denial of service via device reload.
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<= 4.2.3.14<= 4.2.3.14<= 4.2.3.14<= 4.2.3.14<= 1.5.1.11<= 1.5.1.11CVSS 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
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/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 router modelAccess the device web management interface or check physical device label to determine if the model is one of: RV016, RV042, RV042g, RV082, RV320, or RV325Affected if Model is any of the six affected models listed in the CVE
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Check firmware versionLog into the web-based management interface and navigate to System Status or Administration > Firmware Upgrade to view the current firmware version. Compare against affected versions: 4.2.3.14 or lower for RV016/RV042/RV042g/RV082; 1.5.1.11 or lower for RV320/RV325Affected if Installed firmware version is at or below the affected version for that model
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Verify web management interface is enabledCheck device configuration under Administration or Management settings to confirm the web-based management interface is enabledAffected if Web-based management interface is enabled on the device
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Check management interface accessibilityDetermine if the web management interface is accessible from untrusted networks by reviewing access control settings, firewall rules, or WAN-side access configurationAffected if Web management interface is reachable from outside trusted networks or the WAN interface
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Confirm admin accounts existReview user accounts in the Administration or User Management section of the web interface to verify at least one administrator account is configuredAffected if An administrator account is configured and active on the device
The device is likely affected if it is one of the six listed models, runs firmware at or below the specified version limits, and has the web-based management interface accessible with an active admin account.
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-provided firmware patches for affected models; if devices are end-of-life, replace with supported hardware. Restrict web management interface access to trusted networks or disable remote management if not required.
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1339 — 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-2021-1339 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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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.
- 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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