CVE-2021-27257

Downloaded-file tampering via unvalidated FTP certificate

Published Mar 5, 2021 · Updated Aug 3, 2024

Improper certificate validation in NETGEAR R7800 firmware 1.0.2.76 allows network-adjacent attackers to alter files downloaded via FTP. The ready-genie-cloud FTP download path accepts the server certificate without proper validation, permitting an adjacent attacker to substitute downloaded content. No authentication is required; arbitrary root code execution requires chaining the altered download with another vulnerability.

CVSS severity6.5
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in NETGEAR R7800 firmware 1.0.2.76 allows network-adjacent attackers to alter files downloaded via FTP. The ready-genie-cloud FTP download path accepts the server certificate without proper validation, permitting an adjacent attacker to substitute downloaded content. No authentication is required; arbitrary root code execution requires chaining the altered download with another vulnerability.

The record

CVE
CVE-2021-27257
Published
Mar 5, 2021
Updated
Aug 3, 2024
Vendor
NETGEAR
Product
R7800
Classifications
T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=firmware version 1.0.2.76

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

NETGEAR · R7800version=firmware version 1.0.2.76

Published CVSS scores

6.5Zero Day InitiativeCVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A: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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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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