CVE-2019-15971 in AsyncOS
Summary
by MITRE
A vulnerability in the MP3 detection engine of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured content filters on the device. The vulnerability is due to improper validation of certain MP3 file types. An attacker could exploit this vulnerability by sending a crafted MP3 file through the targeted device. A successful exploit could allow the attacker to bypass configured content filters that would normally drop the email.
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Analysis
by VulDB Data Team • 02/28/2024
The vulnerability identified as CVE-2019-15971 resides within the MP3 detection engine of Cisco AsyncOS Software running on Cisco Email Security Appliance devices, representing a critical security flaw that undermines the integrity of email content filtering mechanisms. This weakness specifically targets the validation processes employed by the email security appliance when analyzing incoming MP3 files, creating a pathway for malicious actors to circumvent protective measures that are essential for maintaining secure email communications within enterprise environments.
The technical flaw manifests through insufficient validation of MP3 file characteristics, particularly affecting how the system interprets and processes certain MP3 file types during content inspection. When an attacker crafts a specially formatted MP3 file designed to exploit this validation gap, the system fails to properly identify the file as potentially malicious or non-compliant with configured security policies. This improper validation allows the malicious content to slip through the content filtering mechanisms that would normally detect and block such files, effectively neutralizing the protective capabilities of the email security appliance.
The operational impact of this vulnerability extends beyond simple bypass of content filters, as it fundamentally compromises the security posture of organizations relying on Cisco ESA for email protection. Attackers exploiting this vulnerability can potentially deliver malicious payloads, including malware attachments, phishing content, or other harmful materials that would normally be blocked by the appliance's filtering rules. The remote and unauthenticated nature of the exploit means that attackers do not require valid credentials or physical access to the network, making the vulnerability particularly dangerous as it can be exploited from anywhere on the internet without detection.
Organizations utilizing Cisco Email Security Appliances are particularly vulnerable to this flaw as it directly affects the core functionality of their email security infrastructure, potentially allowing attackers to establish persistent access to corporate email systems. The vulnerability creates a scenario where legitimate security policies designed to prevent unauthorized content delivery become ineffective, leaving organizations exposed to various cyber threats including data exfiltration, malware deployment, and social engineering attacks that leverage email as their primary delivery mechanism.
Mitigation strategies for CVE-2019-15971 should prioritize immediate implementation of Cisco's security patches and updates, while also implementing additional network monitoring to detect anomalous email traffic patterns that might indicate exploitation attempts. Organizations should consider implementing supplementary content filtering measures and conducting thorough security assessments of their email infrastructure to identify potential exploitation vectors. The vulnerability aligns with CWE-20, which addresses "Improper Input Validation," and represents a significant concern from an ATT&CK framework perspective under the T1190 technique for "Exploit Public-Facing Application," highlighting the need for comprehensive application security measures and regular vulnerability assessments to prevent successful exploitation attempts.