CVE detail

CVE-2021-1616 — CVE-2021-1616

Published 2021-09-23 · Modified 2026-06-17 · Vendor cisco · Product ios_xe · Source nvd

MEDIUM

severity

CVSS-derived band

4.7

CVSS v3

0–10 scale

0.0119

EPSS probability

exploitation probability, 30d

65.0%

EPSS percentile

percentile vs all CVEs

NOT LISTED

CISA KEV

known exploited catalog

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.

Remediation

Product	Vulnerable range	Fixed version	Advisory
Cisco Cisco IOS XE Software	—	not specified	advisory ↗

References

cvedb.io · NVD · CISA KEV · FIRST EPSS · vendor advisories (CVE Program List v5). Informational only, no warranty — verify every remediation against the vendor advisory before acting on it. This product uses data from the NVD API but is not endorsed or certified by the NVD, CISA, FIRST.org or any vendor named. CVE® is a registered trademark of The MITRE Corporation.