CVE-2021-20694
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 · uneditedImproper access control vulnerability in DAP-1880AC firmware version 1.21 and earlier allows a remote authenticated attacker to bypass access restriction and to start a telnet service via unspecified vectors.
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 confidenceImproper access control in DAP-1880AC firmware 1.21 and earlier allows a remote authenticated attacker to bypass existing access restrictions and enable a telnet service on the device via unspecified vectors.
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<= 1.21CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 device model and firmware versionAccess the D-Link DAP-1880AC web management interface or check the device label/backup config file for the firmware version string. Look for version information in the administrative console under Status, System Info, or Firmware Upgrade section.Affected if Firmware version is 1.21 or earlier (any version <= 1.21)
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Verify telnet service statusAttempt to connect to the device on TCP port 23 (telnet) from an internal network host using a telnet client or netcat: nc -zv <device_ip> 23. Also check the device web interface for any telnet/SSH service enablement options under Advanced or Administration settings.Affected if Telnet service is listening on any port or shows as enabled in the administrative interface when it was not explicitly configured by the legitimate administrator
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Review access control configurationLog into the D-Link DAP-1880AC web interface and navigate to the Access Control or Security settings section. Check for any unexpected rules that allow remote administrative access, particularly any configuration that permits authenticated users to modify system services.Affected if Access control rules allow remote authenticated users to modify device services, or unauthorized access control entries exist that were not configured by the administrator
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Check for unauthorized administrative sessionsReview any available device logs, system logs, or status pages for telnet connections or administrative sessions from unexpected IP addresses. Look for entries indicating telnet service activation or remote management access.Affected if Logs show telnet connections or administrative actions from untrusted sources, or indicate telnet was enabled outside of normal administrative procedures
A user is affected if the D-Link DAP-1880AC device runs firmware version 1.21 or earlier AND shows evidence of unauthorized telnet service activation or unexpected access control changes.
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 dataUpdate firmware to version 1.22 or later. If patching is not immediately feasible, disable remote administrative access from untrusted networks and monitor for unauthorized telnet service activation.
- Consultation3.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,168.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20694 — 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-2021-20694 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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