CVE-2018-12103
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 · uneditedAn issue was discovered on D-Link DIR-890L with firmware 1.21B02beta01 and earlier, DIR-885L/R with firmware 1.21B03beta01 and earlier, and DIR-895L/R with firmware 1.21B04beta04 and earlier devices (all hardware revisions). Due to the predictability of the /docs/captcha_(number).jpeg URI, being local to the network, but unauthenticated to the administrator's panel, an attacker can disclose the CAPTCHAs used by the access point and can elect to load the CAPTCHA of their choosing, leading to unauthorized login attempts to the access point.
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 confidenceThe D-Link DIR-890L, DIR-885L/R, and DIR-895L routers use a CAPTCHA mechanism with predictable, sequentially numbered file paths (/docs/captcha_N.jpeg). An unauthenticated attacker on the local network can enumerate these files to disclose and load arbitrary CAPTCHAs, enabling brute-force login attempts against the administrator panel.
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<= 1.21b02beta01<= 1.21b03beta01<= 1.21b04beta01CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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 router admin interface or check device label to confirm the exact model number (DIR-890L, DIR-885L, DIR-885R, DIR-895L, or DIR-895R)Affected if Model is one of DIR-890L, DIR-885L/R, or DIR-895L/R
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Check firmware versionLog into router admin panel and navigate to Status or System Info page to view current firmware version, or use router's web interface to retrieve firmware informationAffected if Firmware version is <= 1.21b02beta01 on DIR-890L, <= 1.21b03beta01 on DIR-885L/R, or <= 1.21b04beta01 on DIR-895L/R
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Test CAPTCHA endpoint accessibilityFrom a device on the local network, attempt to access http://routerIP/docs/captcha_1.jpeg and increment the number (e.g., captcha_2.jpeg, captcha_3.jpeg) to verify if CAPTCHA images are sequentially accessible without authenticationAffected if CAPTCHA images load sequentially from /docs/captcha_N.jpeg without requiring login
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Verify admin interface network exposureDetermine if the router admin interface (typically ports 80/443) is reachable from network segments outside the trusted local network, such as guest networks or upstream interfacesAffected if Admin interface is accessible from untrusted network segments beyond the local LAN
The device is affected if it is a DIR-890L, DIR-885L/R, or DIR-895L/R running firmware at or below the specified beta versions AND the /docs/captcha_N.jpeg endpoint is accessible without authentication from an untrusted network segment.
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 router firmware to a version beyond the affected beta releases. If no fixed firmware is available, implement network segmentation or firewall rules to restrict access to the admin interface from untrusted network segments.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12103 — 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-2018-12103 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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