CVE-2021-34746Public exploitNetwork attack vector

Administrator access via TACACS+ parameter injection

Published Sep 2, 2021 · Updated Nov 7, 2024

Authentication bypass in Cisco Enterprise NFV Infrastructure Software 4.5.1 allows remote attackers to gain administrator access. The TACACS+ external-authentication script accepts delimiter characters in credentials and passes an attacker-controlled username to auth_hash.py without safe argument separation, switching the requested operation from authentication to creation of a privilege-level 15 cache entry. TACACS+ external authentication must be enabled; the bypass is reachable over SSH, NETCONF, or HTTPS and grants administrative control of the NFVIS device.

CVSS severity9.8
Critical
EPSS probability17.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Cisco Enterprise NFV Infrastructure Software 4.5.1 allows remote attackers to gain administrator access. The TACACS+ external-authentication script accepts delimiter characters in credentials and passes an attacker-controlled username to auth_hash.py without safe argument separation, switching the requested operation from authentication to creation of a privilege-level 15 cache entry. TACACS+ external authentication must be enabled; the bypass is reachable over SSH, NETCONF, or HTTPS and grants administrative control of the NFVIS device.

The record

CVE
CVE-2021-34746
Published
Sep 2, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Enterprise NFV Infrastructure Software
Classifications
CWE-287, CWE-289, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 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 Enterprise NFV Infrastructure Softwareversion=n/a

Published CVSS scores

9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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
9.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:C/I:C/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.

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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 exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-289Authentication Bypass by Alternate Name
T1190Exploit Public-Facing Application

Public exploit references

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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