CVE-2021-4464
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 · uneditedFiberHome AN5506-04-FA firmware versions up to and including RP2631 and HG6245D prior to RP2602 contain a stack-based buffer overflow, as the HTTP service ('webs') fails to enforce maximum lengths for Cookie header values. When a cookie longer than 511 bytes is processed, a stack buffer is overrun, leading to a crash or potential control of execution flow.
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 confidenceA stack-based buffer overflow vulnerability exists in the FiberHome AN5506-04-FA and HG6245D router firmware HTTP service ('webs'). The web server fails to enforce maximum length restrictions on Cookie header values, allowing an attacker to send cookies exceeding 511 bytes to overrun a fixed-size stack buffer, potentially achieving remote code execution or causing denial of service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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, web interface header, or administrative login page for the exact model number (AN5506-04-FA or HG6245D)Affected if The device is not a FiberHome AN5506-04-FA or HG6245D router, then this CVE does not apply
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Check the firmware versionLog into the router web interface (typically at 192.168.1.1) and look for a Status, System Info, or Firmware Upgrade page that displays the current firmware versionAffected if The firmware version is earlier than RP2602 (e.g., RP2xxx versions below 2602), or the version cannot be determined - the device may be vulnerable
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Verify the HTTP web service is enabledAttempt to access the router's web interface on port 80 or 443 using a browser or curl command (e.g., curl -I http://192.168.1.1)Affected if The web service is disabled or not accessible, the attack surface may be reduced but the vulnerability still exists in the binary if present
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Confirm the vulnerability conditionCompare your identified model and firmware version against the affected range - the vulnerability exists in the 'webs' binary when Cookie header handling does not validate length before copying to a 511-byte stack bufferAffected if The router is an AN5506-04-FA or HG6245D with firmware before RP2602 AND the web service is present - the device is likely affected by this buffer overflow
If you have a FiberHome AN5506-04-FA or HG6245D router with firmware earlier than RP2602 and the HTTP web service is enabled, your device is likely affected by CVE-2021-4464.
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 RP2602 or later which implements proper Cookie header length validation. Until patched, restrict exposure by placing affected devices behind a firewall and disabling remote HTTP management access.
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-4464 — 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-2021-4464 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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