CVE-2021-1495: Cisco IOS XE

Medium severity, CVSS 5.3. EPSS: 1.7% chance of exploitation in the next 30 days.

Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured file policy for HTTP. The vulnerability is due to incorrect handling of specific HTTP header parameters. An attacker could exploit this vulnerability by sending crafted HTTP packets through an affected device. A successful exploit could allow the attacker to bypass a configured file policy for HTTP packets and deliver a malicious payload.

Affected products

• Cisco IOS XE: from 16.12, before 16.12.5 (fixed in 16.12.5); from 17.1, before 17.3.3 (fixed in 17.3.3); from 17.4, before 17.4.1 (fixed in 17.4.1)
• Cisco Secure Firewall Threat Defense: before 6.4.0.12 (fixed in 6.4.0.12); from 6.5.0, before 6.6.4 (fixed in 6.6.4); from 6.7.0, before 6.7.0.2 (fixed in 6.7.0.2)
• Snort Snort: before 2.9.17.1 (fixed in 2.9.17.1)

Published 2021-04-29. Last modified 2026-08-11.