CVE-2021-4464Public exploitNetwork attack vector

Pre-authentication service crash via oversized Cookie header

Published Nov 12, 2025 · Updated Nov 12, 2025

Stack-based buffer overflow in FiberHome AN5506-04-FA and HG6245D firmware allows remote attackers to crash the webs HTTP service. The websParseRequest path processes Cookie values longer than 511 bytes without a maximum-length check, overrunning a stack buffer. Unauthenticated access to any valid ASP page is sufficient; AN5506-04-FA RP2631 and earlier and HG6245D before RP2602 are affected, and the demonstrated consequence is a process crash.

CVSS severity9.3
Critical
EPSS probability2.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in FiberHome AN5506-04-FA and HG6245D firmware allows remote attackers to crash the webs HTTP service. The websParseRequest path processes Cookie values longer than 511 bytes without a maximum-length check, overrunning a stack buffer. Unauthenticated access to any valid ASP page is sufficient; AN5506-04-FA RP2631 and earlier and HG6245D before RP2602 are affected, and the demonstrated consequence is a process crash.

The record

CVE
CVE-2021-4464
Published
Nov 12, 2025
Updated
Nov 12, 2025
Vendor
FiberHome
Product
HG6245D
Classifications
CWE-121, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 12, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <RP2602

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FiberHome · HG6245Dversion=0 <RP2602
FiberHome · AN5506-04-FAversion=0 <=RP2631

Published CVSS scores

9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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