CVE-2021-27253

Root code execution via rc_service heap overflow

Published Apr 14, 2021 · Updated Aug 3, 2024

Heap-based buffer overflow in NETGEAR R7800 firmware 1.0.2.76 allows remote attackers to execute arbitrary code as root. apply_bind.cgi fails to validate the user-controlled rc_service parameter before passing it to a system call, overflowing a heap buffer. Attackers must reach the router from an adjacent network; the required authentication can be bypassed, enabling full control with root privileges.

CVSS severity8.8
High
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in NETGEAR R7800 firmware 1.0.2.76 allows remote attackers to execute arbitrary code as root. apply_bind.cgi fails to validate the user-controlled rc_service parameter before passing it to a system call, overflowing a heap buffer. Attackers must reach the router from an adjacent network; the required authentication can be bypassed, enabling full control with root privileges.

The record

CVE
CVE-2021-27253
Published
Apr 14, 2021
Updated
Aug 3, 2024
Vendor
NETGEAR
Product
R7800
Classifications
CWE-787, CWE-122, T1190
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 14, 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

8.3NISTAV:A/AC:L/Au:N/C:C/I:C/A:C
8.8Zero Day InitiativeCVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.8NISTCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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

CWE-787Out-of-bounds Write
CWE-122Heap-based Buffer Overflow
T1190Exploit Public-Facing Application

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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