CVE-2021-34727

highpriority · track · 40EPSS 0.026 · 85 %ileEURUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

2.63% (85th) EPSS

CVSS 10 · high

Is it mine?

33 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · cisco_csaf

EPSS · scored 2026-10-27

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.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 1000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco 4000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco ASR 1000 Series Aggregation Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Catalyst IR1100 Rugged Series Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Cloud Services Router 1000V Seriescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1b when installed on Cisco Integrated Services Virtual Routercisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 1000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco 4000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco ASR 1000 Series Aggregation Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Catalyst IR1100 Rugged Series Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Cloud Services Router 1000V Seriescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1d when installed on Cisco Integrated Services Virtual Routercisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco 1000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco 4000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco ASR 1000 Series Aggregation Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Catalyst IR1100 Rugged Series Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Cloud Services Router 1000V Seriescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.1e when installed on Cisco Integrated Services Virtual Routercisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco 1000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco 4000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco ASR 1000 Series Aggregation Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Catalyst IR1100 Rugged Series Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Cloud Services Router 1000V Seriescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.2r when installed on Cisco Integrated Services Virtual Routercisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco 1000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco 4000 Series Integrated Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco ASR 1000 Series Aggregation Services Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Catalyst IR1100 Rugged Series Routerscisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Cloud Services Router 1000V Seriescisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com
FixedCisco IOS XE Catalyst SD-WAN 16.12.3 when installed on Cisco Integrated Services Virtual Routercisco_csaf
Cisco has released software updates that address this vulnerability.
https://software.cisco.com

cvss

Technical severity, 0–10. One row per scoring source.

10.0

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 9–10

v2.010highAV:N/AC:L/Au:N/C:C/I:C/A:Cprimary · NVD / NIST USexploitability 10 · impact 10

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9

v3.19.8criticalAV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · ENISA EU

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · psirt@cisco.com USexploitability 3.9 · impact 5.9

v3.19criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · Cisco PSIRT US

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-120USprimaryCWE-120US

affected products (33)

Products and version ranges known to be affected.

showing 20 of 33

advisories (1)

Vendor and ecosystem advisories describing this.

cisco-sa-iosxesdwan-rbuffover-vE2OB6tpCisco IOS XE SD-WAN Software Buffer Overflow Vulnerability2021-09-22csaf · cisco_csafUS
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"]

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cisco_csaf NVD CVE.org MITRE

published 2021-09-23modified 2026-06-17

related (5,669)

Related entries.

ID	severity	EPSS	exploitable	published
CVE-2025-43520US	medium5.5OT critical	0.43% (37th)	KEV	2025-12-12
A memory corruption issue was addressed with improved memory handling. This issue is fixed in iOS 18.7.2 and iPadOS 18.7.2, iOS 26.1 and iPadOS 26.1, macOS Sequoia 15.7.2, macOS So…
CVE-2025-20333US	—OT critical	71.2% (99th)	KEV	2025-09-25
A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an aut…
CVE-2025-39682US	critical9.8OT critical	3.25% (88th)	KEV	2025-09-05
In the Linux kernel, the following vulnerability has been resolved: tls: fix handling of zero-length records on the rx_list Each recvmsg() call must process either - only contig…
CVE-2025-31277US	—OT critical	1.66% (77th)	KEV	2025-07-30
The issue was addressed with improved memory handling. This issue is fixed in Safari 18.6, iOS 18.6 and iPadOS 18.6, macOS Sequoia 15.6, tvOS 18.6, visionOS 2.6, watchOS 11.6. Proc…
CVE-2025-24985US	—OT critical	3.89% (90th)	KEV	2025-03-11
Integer overflow or wraparound in Windows Fast FAT Driver allows an unauthorized attacker to execute code locally.

+5664 more

references (7)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan