CVE-2021-1495: 
Snort vulnerability analysis and mitigation

CVE-2021-1495 is a vulnerability in the Snort detection engine that affects multiple Cisco products, discovered and disclosed in April 2021. The vulnerability allows an unauthenticated, remote attacker to bypass a configured file policy for HTTP. This issue affects various Cisco products including 1000 Series ISRs, 3000 Series ISAs, 4000 Series ISRs, and Firepower Threat Defense (FTD) Software, as well as all open source Snort project releases earlier than Release 2.9.17.1 (Cisco Advisory).

The vulnerability stems from incorrect handling of specific HTTP header parameters. The issue has been assigned a CVSS Base Score of 5.8 (Medium) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N, indicating network accessibility, low attack complexity, and no required privileges or user interaction (Cisco Advisory).

A successful exploitation of this vulnerability could allow an attacker to bypass a configured file policy for HTTP packets and deliver a malicious payload. This could potentially lead to unauthorized file transfers or malware delivery through affected devices (NVD).

Cisco has released software updates that address this vulnerability. For Cisco FTD Software, fixed versions include 6.4.0.12, 6.6.4, and 6.7.0.2. For Cisco IOS XE Software, fixes are available in versions 16.12.5, 17.3.3, and 17.4.1. For open source Snort, the fix is included in version 2.9.17.1 and later. No workarounds are available for this vulnerability (Cisco Advisory).