How severe is CVE-2021-34787?

CVE-2021-34787 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-34787 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34787?

CVE-2021-34787 primarily affects Cisco Adaptive Security Appliance. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34787?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-34787 published?

CVE-2021-34787 was published on 2021-10-27 and last updated on 2026-06-17.

CVE-2021-34787

CVE-2021-34787 is a medium-severity vulnerability in Cisco Adaptive Security Appliance with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 4.3
EPSS exploit prediction: 1% (59th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Cisco Adaptive Security Appliance
Published: 2021-10-27
Last modified: 2026-06-17

Description

A vulnerability in the identity-based firewall (IDFW) rule processing feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass security protections. This vulnerability is due to improper handling of network requests by affected devices configured to use object group search. An attacker could exploit this vulnerability by sending a specially crafted network request to an affected device. A successful exploit could allow the attacker to bypass access control list (ACL) rules on the device, bypass security protections, and send network traffic to unauthorized hosts.

Frequently asked questions

What is CVE-2021-34787?: A vulnerability in the identity-based firewall (IDFW) rule processing feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass security protections. This vulnerability is due to improper handling of network requests by affected devices configured to use object group search. An attacker could exploit this vulnerability by sending a specially crafted network request to an affected device. A successful exploit could allow the attacker to bypass access control list (ACL) rules on the device, bypass security protections, and send network traffic to unauthorized hosts.
How severe is CVE-2021-34787?: CVE-2021-34787 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-34787 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (59th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34787?: CVE-2021-34787 primarily affects Cisco Adaptive Security Appliance. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34787?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-34787 published?: CVE-2021-34787 was published on 2021-10-27 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-rule-bypass-ejjOgQEY

Affected products (19)

cpe:2.3:a:cisco:adaptive_security_appliance:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5512-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5512-x_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5505_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5505_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5515-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5515-x_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5525-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5525-x_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5545-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5545-x_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5555-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5555-x_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5580_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5580_firmware:009.012:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5585-x_firmware:009.009:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5585-x_firmware:009.012:*:*:*:*:*:*:*

More vulnerabilities in Cisco Adaptive Security Appliance

CVE-2021-1573 — High (CVSS 8.6): A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower…
CVE-2021-40118 — High (CVSS 8.6): A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower…
CVE-2021-40117 — High (CVSS 8.6): A vulnerability in SSL/TLS message handler for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower…
CVE-2021-34793 — High (CVSS 8.6): A vulnerability in the TCP Normalizer of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense…
CVE-2020-3572 — High (CVSS 8.6): A vulnerability in the SSL/TLS session handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower…
CVE-2020-3529 — High (CVSS 8.6): A vulnerability in the SSL VPN negotiation process for Cisco Adaptive Security Appliance (ASA) Software and Cisco…

All CVEs affecting Cisco Adaptive Security Appliance →

Other CWE-755 (Improper Handling of Exceptional Conditions) vulnerabilities

CVE-2025-34193 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) Virtual Appliance Host versions prior to 25.1.102 and Application versions prior…
CVE-2025-10156 — Critical (CVSS 9.8): An Improper Handling of Exceptional Conditions vulnerability in the ZIP archive scanning component of mmaitre314…
CVE-2021-42142 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. DTLS servers mishandle the early use of a…
CVE-2021-42141 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through 2018-08-30. One incorrect handshake could complete with…
CVE-2023-38406 — Critical (CVSS 9.8): bgpd/bgp_flowspec.c in FRRouting (FRR) before 8.4.3 mishandles an nlri length of zero, aka a "flowspec overflow."
CVE-2022-23121 — Critical (CVSS 9.8): This vulnerability allows remote attackers to execute arbitrary code on affected installations of Netatalk.…

Browse all CWE-755 (Improper Handling of Exceptional Conditions) vulnerabilities →