CVE-2021-1376

Privileged code execution via improper boot configuration verification

Published Mar 24, 2021 · Updated Nov 8, 2024

Code execution in the fast reload feature of Cisco IOS XE Software allows local users to run arbitrary code on the underlying OS. Boot configuration verification performs an improper check during the initial fast reload boot process instead of fully validating the configuration file. Exploitation requires privileged CLI access on an affected Catalyst switch and exposes the underlying operating system to attacker-controlled code.

CVSS severity5.1
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code execution in the fast reload feature of Cisco IOS XE Software allows local users to run arbitrary code on the underlying OS. Boot configuration verification performs an improper check during the initial fast reload boot process instead of fully validating the configuration file. Exploitation requires privileged CLI access on an affected Catalyst switch and exposes the underlying operating system to attacker-controlled code.

The record

CVE
CVE-2021-1376
Published
Mar 24, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco IOS XE Software
Classifications
CWE-347, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 24, 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 vectorlocal
Required privilegesadmin

What is affected?

ClamAV · Cisco IOS XE Softwareversion=n/a

Published CVSS scores

7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C
6.7NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
5.1Cisco Systems, Inc.CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:H/A:N

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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