CVE-2021-1273Network attack vector

Service interruption via IPSec forwarding-plane bounds failure

Published Jan 20, 2021 · Updated Nov 12, 2024

Bounds-checking failure in Cisco SD-WAN IPSec tunnel management allows remote attackers to interrupt affected devices with crafted IP packets. The forwarding plane performs inadequate bounds checking while processing crafted IPv4 or IPv6 packets for IPSec tunnel management. No authentication or user interaction is required, and Cisco reports a denial-of-service condition without specifying whether the device crashes or reboots.

CVSS severity8.6
High
EPSS probability1.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Bounds-checking failure in Cisco SD-WAN IPSec tunnel management allows remote attackers to interrupt affected devices with crafted IP packets. The forwarding plane performs inadequate bounds checking while processing crafted IPv4 or IPv6 packets for IPSec tunnel management. No authentication or user interaction is required, and Cisco reports a denial-of-service condition without specifying whether the device crashes or reboots.

The record

CVE
CVE-2021-1273
Published
Jan 20, 2021
Updated
Nov 12, 2024
Vendor
ClamAV
Product
Cisco SD-WAN
Classifications
CWE-119, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 12, 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 SD-WANversion=n/a

Published CVSS scores

8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.8NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499Endpoint Denial of Service

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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