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ReviewHigh

CVE-2021-34793

Cisco Cisco Adaptive Security Appliance (ASA) Software, adaptive security appliance, secure firewall threat defense

A vulnerability in the TCP Normalizer of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software operating in transparent mode could allow an unauthenticated, remote attacker to poison MAC address tables, resulting in a denial of service (DoS) vulnerability. This vulnerability is due to incorrect handling of certain TCP segments when the affected device is operating in transparent mode. An attacker could exploit this vulnerability by sending a crafted TCP segment through an affected device. A successful exploit could allow the attacker to poison the MAC...

CVSS
8.6
EPSS
0.67%
49.6% percentile
CISA KEV
Not listed
Published
2021.10.28
PRIORITY ASSESSMENT

Review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.67%
Technical severityCVSS 8.6

Vulnerability overview

A vulnerability in the TCP Normalizer of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software operating in transparent mode could allow an unauthenticated, remote attacker to poison MAC address tables, resulting in a denial of service (DoS) vulnerability. This vulnerability is due to incorrect handling of certain TCP segments when the affected device is operating in transparent mode. An attacker could exploit this vulnerability by sending a crafted TCP segment through an affected device. A successful exploit could allow the attacker to poison the MAC...

Affected product and versions

Product
Cisco Cisco Adaptive Security Appliance (ASA) Software, adaptive security appliance, secure firewall threat defense
Affected versions
< 9.8.4.40, < 6.4.0.13, >= 6.5.0 < 6.6.5, >= 6.7.0 < 6.7.0.3, >= 9.9.0 < 9.12.4.29, >= 9.13.0 < 9.14.3.9, >= 9.15.0 < 9.15.1.17, >= 9.16.0 < 9.16.2.3, 009.008(004.025)
Fixed versions
9.8.4.40, 6.4.0.13, 6.6.5, 6.7.0.3, 9.12.4.29, 9.14.3.9, 9.15.1.17, 9.16.2.3

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Cisco Cisco Adaptive Security Appliance (ASA) Software, adaptive security appliance, secure firewall threat defense and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CWE
CWE-924