CVE-2021-34727Network attack vector

Root command execution via vDaemon buffer overflow

Published Sep 23, 2021 · Updated Nov 7, 2024

Buffer overflow in the vDaemon process of Cisco IOS XE SD-WAN Software allows remote attackers to execute root commands or reload devices. vDaemon performs insufficient bounds checking while processing crafted network traffic, allowing attacker-controlled data to overflow a buffer. The SD-WAN feature must be enabled, and exploitation grants root-level command execution or forces a device reload.

CVSS severity9.8
Critical
EPSS probability2.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in the vDaemon process of Cisco IOS XE SD-WAN Software allows remote attackers to execute root commands or reload devices. vDaemon performs insufficient bounds checking while processing crafted network traffic, allowing attacker-controlled data to overflow a buffer. The SD-WAN feature must be enabled, and exploitation grants root-level command execution or forces a device reload.

The record

CVE
CVE-2021-34727
Published
Sep 23, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco IOS XE SD-WAN Software
Classifications
CWE-120, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 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 privilegesunauthenticated

What is affected?

ClamAV · Cisco IOS XE SD-WAN Softwareversion=n/a

Published CVSS scores

10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C
9.8Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic 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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