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ReviewHigh

CVE-2021-34783

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

A vulnerability in the software-based SSL/TLS message handler of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL/TLS decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message to an affected device. A successful exploit could allow the attacker to cause the affec...

CVSS
7.5
EPSS
1.60%
74.1% 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 probability1.60%
Technical severityCVSS 7.5

Vulnerability overview

A vulnerability in the software-based SSL/TLS message handler of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL/TLS decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message to an affected device. A successful exploit could allow the attacker to cause the affec...

Affected product and versions

Product
Cisco Cisco Adaptive Security Appliance (ASA) Software, secure firewall threat defense, adaptive security appliance software
Affected versions
>= 6.4.0 < 6.4.0.13, >= 6.6.0 < 6.6.5, >= 6.7.0 < 6.7.0.3, >= 7.0.0 < 7.0.1, >= 9.8.0 < 9.8.4.40, >= 9.12.0 < 9.12.4.29, >= 9.14.0 < 9.14.3.9, >= 9.15.0 < 9.15.1.17, >= 9.16.0 < 9.16.2, 009.016(001), 009.016(001.025)
Fixed versions
6.4.0.13, 6.6.5, 6.7.0.3, 7.0.1, 9.8.4.40, 9.12.4.29, 9.14.3.9, 9.15.1.17, 9.16.2

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, secure firewall threat defense, adaptive security appliance software 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:U/C:N/I:N/A:H
CWE
CWE-119, CWE-20