CVE-2020-3315 in Product
Summary
by MITRE
Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass the configured file policies on an affected system. The vulnerability is due to errors in how the Snort detection engine handles specific HTTP responses. An attacker could exploit this vulnerability by sending crafted HTTP packets that would flow through an affected system. A successful exploit could allow the attacker to bypass the configured file policies and deliver a malicious payload to the protected network.
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Analysis
by VulDB Data Team • 10/15/2020
The vulnerability identified as CVE-2020-3315 represents a critical weakness in Cisco's Snort detection engine implementation that undermines network security policies. This flaw affects multiple Cisco products including firewalls, intrusion prevention systems, and security appliances that utilize Snort as their core detection mechanism. The vulnerability stems from improper handling of HTTP responses within the Snort engine, creating a pathway for malicious actors to circumvent established security controls. Security professionals must understand that this issue directly impacts the integrity of file filtering policies that organizations rely upon to prevent unauthorized content delivery. The flaw demonstrates how seemingly minor implementation errors in security software can result in significant operational risks when exploited by threat actors.
The technical exploitation of CVE-2020-3315 occurs through carefully crafted HTTP packets that exploit parsing inconsistencies in the Snort detection engine. When affected systems process these malicious packets, the engine fails to properly evaluate the HTTP response headers and content, allowing attackers to bypass configured file policy restrictions. This vulnerability operates at the network protocol level where HTTP traffic flows through Cisco security appliances, making it particularly dangerous as it can affect both inbound and outbound traffic. The flaw specifically manifests when the Snort engine encounters certain combinations of HTTP response codes and header values that it cannot properly classify or filter. This misclassification enables malicious payloads to slip through security controls that should have blocked them based on predefined file type policies.
From an operational perspective, successful exploitation of CVE-2020-3315 could result in significant security breaches where attackers deliver malicious payloads that would normally be blocked by file filtering policies. Organizations using affected Cisco products face the risk of data exfiltration, malware delivery, and potential lateral movement within their networks. The vulnerability is particularly concerning because it allows unauthenticated remote access without requiring prior system compromise or credentials. Network administrators may not immediately detect such attacks since the malicious traffic appears to comply with configured policies, making this a stealthy threat vector. This type of vulnerability directly impacts the CIA triad by potentially compromising confidentiality and integrity of network communications, while also affecting availability through potential service disruption.
Organizations should implement immediate mitigations including applying Cisco's security patches and updates that address the Snort engine parsing errors. Network segmentation and additional monitoring controls should be deployed to detect anomalous HTTP traffic patterns that might indicate exploitation attempts. Security teams should review and validate existing file filtering policies to ensure they properly account for potential bypass scenarios. The vulnerability aligns with CWE-129, which addresses improper handling of input boundaries, and relates to ATT&CK technique T1071.004 for application layer protocol traffic. Additionally, this issue maps to ATT&CK tactic TA0011, which covers command and control operations, as attackers could use this vulnerability to establish covert communication channels. Organizations should also consider implementing network behavior analysis tools that can detect deviations from normal HTTP traffic patterns, as traditional signature-based detection may not identify this specific exploitation method.