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Fencer Vulns
high 8.6

CVE-2021-1501 json

Cisco Adaptive Security Appliance Software and Cisco Firepower Threat Defense Software SIP Denial of Service Vulnerability

published 2021-04-29 5 y ago modified 2026-08-11 2 mo ago also EUVD-2021-6968

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

A vulnerability in the SIP inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affected device, resulting in a denial of service (DoS) condition.The vulnerability is due to a crash that occurs during a hash lookup for a SIP pinhole connection. An attacker could exploit this vulnerability by sending crafted SIP traffic through an affected device. A successful exploit could allow the attacker to cause a crash and reload of the affected device.

Patch / fix

  • cisco secure_firewall_threat_defense 6.4.0.12, 6.6.4, 6.7.0.2
  • cisco adaptive_security_appliance_software 9.8.4.34, 9.9.2.85, 9.12.4.18, 9.13.1.21, 9.14.2.13, 9.15.1.15

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.35% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C

Affected products

  • Cisco Cisco Adaptive Security Appliance (ASA) Software

Classification

Weakness
  • CWE-613 DEPRECATED: Insufficient Session Expiration

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.