CVE-2025-20359 is a vulnerability identified in the Snort 3 HTTP Decoder component integrated within Cisco Cyber Vision products. The root cause is a logic error in buffer handling when parsing MIME fields in HTTP headers, leading to a buffer under-read condition. This flaw allows an unauthenticated remote attacker to craft malicious HTTP packets that, when processed by Snort 3, can cause two primary adverse outcomes: (1) a denial of service (DoS) by forcing the Snort 3 Detection Engine to crash and restart unexpectedly, and (2) potential disclosure of sensitive information from the Snort 3 data stream due to reading memory outside of valid buffers. The vulnerability affects a broad range of Cisco Cyber Vision versions from 3.0.0 through 5.2.1, indicating a long-standing issue across multiple releases. The CVSS v3.1 base score is 6.5 (medium severity), reflecting the vulnerability's network attack vector, lack of required privileges or user interaction, and its impact primarily on confidentiality (partial data disclosure) and availability (DoS). No known exploits have been reported in the wild as of the publication date, but the vulnerability's nature makes it a candidate for exploitation in environments where Cisco Cyber Vision is deployed for industrial network visibility and security monitoring. The vulnerability's exploitation could disrupt security monitoring capabilities and expose sensitive operational data, undermining the integrity of industrial control system defenses.

For European organizations, especially those in critical infrastructure sectors such as manufacturing, energy, and utilities that rely on Cisco Cyber Vision for industrial network monitoring, this vulnerability poses a significant risk. A successful exploit could lead to denial of service conditions, temporarily disabling security monitoring and detection capabilities, which could allow attackers to operate undetected or cause operational disruptions. Additionally, the potential disclosure of sensitive information from the Snort 3 data stream could expose proprietary or operational data, increasing the risk of industrial espionage or targeted attacks. The impact is heightened in environments where continuous monitoring is essential for compliance with regulations such as NIS2 and GDPR, as any data leakage or monitoring downtime could lead to regulatory penalties and reputational damage. The broad range of affected versions suggests many organizations may be vulnerable if patches are not applied promptly. The lack of authentication requirement lowers the barrier for exploitation, increasing the urgency for mitigation.

Organizations should immediately identify and inventory all Cisco Cyber Vision deployments and verify the software versions in use. Applying vendor-provided patches or updates that address CVE-2025-20359 is the most effective mitigation. If patches are not yet available, organizations should consider temporary network-level controls such as filtering or blocking suspicious HTTP traffic targeting the Snort 3 HTTP Decoder, especially crafted packets with unusual MIME headers. Implementing strict network segmentation to isolate industrial monitoring systems from general IT networks and the internet can reduce exposure. Continuous monitoring for unusual Snort 3 Detection Engine restarts or anomalies in HTTP traffic can provide early warning of exploitation attempts. Additionally, reviewing and tightening access controls around Cisco Cyber Vision management interfaces and ensuring that only authorized personnel can modify configurations will help reduce risk. Finally, organizations should prepare incident response plans that include scenarios involving DoS or data leakage from monitoring systems to minimize operational impact.