CVE-2025-6599
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 uncontrolled resource consumption vulnerability in the web server of Zyxel DX3301-T0 firmware version 5.50(ABVY.6.3)C0 and earlier could allow an attacker to perform Slowloris‑style denial‑of‑service (DoS) attacks. Such attacks may temporarily block legitimate HTTP requests and partially disrupt access to the web management interface, while other networking services remain unaffected.
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 Zyxel DX3301-T0 router's web server has an uncontrolled resource consumption vulnerability that allows Slowloris-style DoS attacks. Attackers can exhaust HTTP connection resources by sending incomplete requests and holding connections open, temporarily blocking legitimate HTTP access to the web 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<= 1.00\(abqu.7\)c0<= 4.19\(abyc.8\)c0<= 1.00\(acdj.1\)c0<= 1.00\(ackp.1\)b3<= 5.00\(acha.5\)c0<= 1.00\(acei.1\)c0<= 1.19\(acko.0\)c0<= 1.20\(acgd.1\)c0CVSS 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
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 router modelCheck the device label or web interface for the exact model number (Lte3301 Plus, Nr5103, Nr5103e, Nr5309, Nr7302, Nr7303, Nebula Fwa505, or Nebula Fwa510)Affected if The model is one of the eight affected products listed in the CVE
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Check the installed firmware versionAccess the router web interface (typically at 192.168.1.1 or 192.168.0.1), navigate to Status or System Info page, and note the firmware version string (e.g., 1.00(abqu.7)c0)Affected if The firmware version is at or below the version numbers specified for that model in the CVE
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Verify web management interface is exposedConfirm the router's HTTP (port 80) or HTTPS (port 443) web interface is accessible from the network where attackers could reach itAffected if The web management interface is internet-facing or accessible from untrusted networks
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Monitor for connection exhaustion symptomsCheck the router's concurrent HTTP connection count or observe that legitimate users cannot access the web interface during suspected attack periodsAffected if HTTP connections cannot be established or the web interface becomes unresponsive under normal use conditions
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Compare version to fixed releaseConsult Zyxel support or release notes to determine if a newer firmware beyond the affected versions is available for your modelAffected if Your current firmware version is within the affected ranges and no fixed version has been applied
You are affected if you run any of the eight listed Zyxel router models with firmware at or below the specified version numbers and the web management interface is network-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 dataUpdate the firmware to a version beyond 5.50(ABVY.6.3)C0. If immediate patching is not possible, consider implementing network-level rate limiting or HTTP connection thresholds to mitigate the attack vector.
- 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-2025-6599 — 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-2025-6599 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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