CVE-2021-34739Network attack vector

Administrator access via replayed session credentials

Published Nov 4, 2021 · Updated Nov 7, 2024

Session credential replay in Cisco Small Business Smart and Managed Switches allows remote attackers to obtain administrator access. The web-based management interface fails to expire valid session credentials, allowing intercepted tokens to be replayed later against the same device. Exploitation requires a man-in-the-middle position during a valid user session and grants administrator privileges in the management interface.

CVSS severity8.1
High
EPSS probability1.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Session credential replay in Cisco Small Business Smart and Managed Switches allows remote attackers to obtain administrator access. The web-based management interface fails to expire valid session credentials, allowing intercepted tokens to be replayed later against the same device. Exploitation requires a man-in-the-middle position during a valid user session and grants administrator privileges in the management interface.

The record

CVE
CVE-2021-34739
Published
Nov 4, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Small Business Smart and Managed Switches
Classifications
CWE-613, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 4, 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?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Small Business Smart and Managed Switchesversion=n/a

Published CVSS scores

8.1CiscoCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration
T1550.004Use Alternate Authentication Material: Web Session Cookie

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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