---
id: CVE-2021-34727
title: Cisco IOS XE SD-WAN Software Buffer Overflow Vulnerability (CVE-2021-34727)
summary: "A vulnerability in the vDaemon process in Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a buffer overflow on an affected device.\r\n\r\nThis vulnerability is due to insufficient bounds checking when an a…"
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: vendor
vendor: Cisco
product: Cisco 4000 Series Integrated Services Routers
affected:
  - cloud_services_router_1000v_series
  - 1000_series_integrated_services_routers
  - asr_1000_series_aggregation_services_routers
  - 4000_series_integrated_services_routers
  - integrated_services_virtual_router
  - 1100_series_industrial_integrated_services_routers
published: '2021-09-22'
updated: '2021-09-22'
sourceUpdated: '2021-09-22T16:00:00+00:00'
source: CSAF
sourceUrl: >-
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxesdwan-rbuffover-vE2OB6tp
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxesdwan-rbuffover-vE2OB6tp
  - url: 'https://software.cisco.com'
tags:
  - csaf
  - vendor-advisory
  - cisco
epss: 0.02629
epssPercentile: 0.84888
ingestedAt: '2026-09-25T07:41:37.790Z'
---

## Overview

A vulnerability in the vDaemon process in Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a buffer overflow on an affected device.

This vulnerability is due to insufficient bounds checking when an affected device processes traffic. An attacker could exploit this vulnerability by sending crafted traffic to the device. A successful exploit could allow the attacker to cause a buffer overflow and possibly execute arbitrary commands with root-level privileges, or cause the device to reload, which could result in a denial of service condition.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.



This advisory is part of the September 2021 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication. ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-74581"]

## Vendor advisories

- **cisco-sa-iosxesdwan-rbuffover-vE2OB6tp** · Cisco · affected: Cisco Cloud Services Router 1000V Series, Cisco 1000 Series Integrated Services Routers, Cisco ASR 1000 Series Aggregation Services Routers, Cisco 4000 Series Integrated Services Routers, Cisco Integrated Services Virtual Router, Cisco 1100 Series Industrial Integrated Services Routers · updated 2021-09-22 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxesdwan-rbuffover-vE2OB6tp)

**Cisco IOS XE SD-WAN Software Buffer Overflow Vulnerability**. Released 2021-09-22.

Affected:

- Cisco Cloud Services Router 1000V Series
- Cisco 1000 Series Integrated Services Routers
- Cisco ASR 1000 Series Aggregation Services Routers
- Cisco 4000 Series Integrated Services Routers
- Cisco Integrated Services Virtual Router
- Cisco 1100 Series Industrial Integrated Services Routers

## Remediation

Cisco has released software updates that address this vulnerability. https://software.cisco.com