VULNERABILITY INTELLIGENCE

CVE-2021-1616

CVSS score4.7 MEDIUM
EPSS probability1.19%
CISA KEVNot currently listed
Published2021-09-23
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Description

A vulnerability in the H.323 application level gateway (ALG) used by the Network Address Translation (NAT) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass the ALG. This vulnerability is due to insufficient data validation of traffic that is traversing the ALG. An attacker could exploit this vulnerability by sending crafted traffic to a targeted device. A successful exploit could allow the attacker to bypass the ALG and open connections that should not be allowed to a remote device located behind the ALG. Note: This vulnerability has been publicly discussed as NAT Slipstreaming.

Weakness classification

  • psirt@cisco.com: CWE-693
  • nvd@nist.gov: NVD-CWE-Other

Primary references