CVE-2021-1167Public exploitNetwork attack vector

Root code execution or reload via vpn_account overflow

Published Jan 13, 2021 · Updated Nov 8, 2024

Stack overflow in Cisco Small Business RV router firmware allows remote authenticated users to execute root code or reload the device. The web management interface's vpn_account handler fails to bound administrator-supplied HTTP input, overflowing its stack. Valid administrator credentials are required, and WAN exposure exists only when remote management is enabled; local-LAN access remains available.

CVSS severity7.2
High
EPSS probability5.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack overflow in Cisco Small Business RV router firmware allows remote authenticated users to execute root code or reload the device. The web management interface's vpn_account handler fails to bound administrator-supplied HTTP input, overflowing its stack. Valid administrator credentials are required, and WAN exposure exists only when remote management is enabled; local-LAN access remains available.

The record

CVE
CVE-2021-1167
Published
Jan 13, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco Small Business RV Series Router Firmware
Classifications
CWE-121, CWE-787, T1190, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jan 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

ClamAV · Cisco Small Business RV Series Router Firmwareversion=n/a

Published CVSS scores

7.2Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-787Out-of-bounds Write
T1190Exploit Public-Facing Application
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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