CVE-2021-34787Network attack vector

Unauthenticated ACL bypass via object group search

Published Oct 27, 2021 · Updated Nov 7, 2024

Identity-based firewall rule processing in Cisco Adaptive Security Appliance Software allows remote attackers to bypass ACL protections via crafted network requests. The IDFW handler misprocesses requests when rules use object group search, allowing traffic to hosts that ACLs should deny. Exploitation requires the device to use object-group-search IDFW rules; Cisco reports no public malicious use, and the consequence is unauthorized network access rather than device takeover.

CVSS severity5.3
Medium
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Identity-based firewall rule processing in Cisco Adaptive Security Appliance Software allows remote attackers to bypass ACL protections via crafted network requests. The IDFW handler misprocesses requests when rules use object group search, allowing traffic to hosts that ACLs should deny. Exploitation requires the device to use object-group-search IDFW rules; Cisco reports no public malicious use, and the consequence is unauthorized network access rather than device takeover.

The record

CVE
CVE-2021-34787
Published
Oct 27, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-183, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 27, 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 Adaptive Security Appliance (ASA) Softwareversion=n/a

Published CVSS scores

5.3Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
4.3National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:P/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.

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-183Improper Validation of Specified Quantity in Input
T1190Exploit Public-Facing Application

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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