Medium severity4.7NVD Advisory· Published Oct 27, 2021· Updated Aug 11, 2026

CVE-2021-34790

Description

Multiple vulnerabilities in the Application Level Gateway (ALG) for the Network Address Translation (NAT) feature of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass the ALG and open unauthorized connections with a host located behind the ALG. For more information about these vulnerabilities, see the Details section of this advisory. Note: These vulnerabilities have been publicly discussed as NAT Slipstreaming.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

Cisco Systems, Inc./Cisco Adaptive Security Appliance2 versions
cpe:2.3:a:cisco:adaptive_security_appliance:*:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:a:cisco:adaptive_security_appliance:*:*:*:*:*:*:*:*range: <9.8.4.40
- cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*range: >=9.12.0,<9.12.4.29
Cisco Systems, Inc./Secure Firewall Threat Defense
cpe:2.3:a:cisco:secure_firewall_threat_defense:*:*:*:*:*:*:*:*
Range: <6.4.0.12
Cisco Systems, Inc./Asa 5505 Firmware2 versions
cpe:2.3:o:cisco:asa_5505_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5505_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5505_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5512 X Firmware2 versions
cpe:2.3:o:cisco:asa_5512-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5512-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5512-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5515 X Firmware2 versions
cpe:2.3:o:cisco:asa_5515-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5515-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5515-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5525 X Firmware2 versions
cpe:2.3:o:cisco:asa_5525-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5525-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5525-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5545 X Firmware2 versions
cpe:2.3:o:cisco:asa_5545-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5545-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5545-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5555 X Firmware2 versions
cpe:2.3:o:cisco:asa_5555-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5555-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5555-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5580 Firmware2 versions
cpe:2.3:o:cisco:asa_5580_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5580_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5580_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Asa 5585 X Firmware2 versions
cpe:2.3:o:cisco:asa_5585-x_firmware:009.008:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:o:cisco:asa_5585-x_firmware:009.008:*:*:*:*:*:*:*
- cpe:2.3:o:cisco:asa_5585-x_firmware:009.015:*:*:*:*:*:*:*
Cisco Systems, Inc./Adaptive Security Appliance (ASA) Softwarellm-fuzzy
Cisco Systems, Inc./Firepower Threat Defense Softwarellm-fuzzy
Cisco Systems, Inc./Adaptive Security Appliance Cx Context Aware Security Softwarecpe-rescue
Range: n/a

Patches

Vulnerability mechanics

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-natalg-bypass-cpKGqkngnvdVendor Advisory

News mentions

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