CVE-2025-20327 in IOS
Summary
by MITRE • 09/24/2025
A vulnerability in the web UI of Cisco IOS Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to improper input validation. An attacker could exploit this vulnerability by sending a crafted URL in an HTTP request. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 09/24/2025
The vulnerability identified as CVE-2025-20327 represents a significant security flaw within Cisco IOS Software that affects the web user interface component. This issue stems from inadequate input validation mechanisms that fail to properly sanitize or verify user-supplied data before processing. The vulnerability specifically manifests in the web UI handling of HTTP requests, where the system does not adequately validate the structure or content of URLs submitted by users. This weakness creates an exploitable entry point for malicious actors who can manipulate the web interface to trigger unintended system behavior.
The technical exploitation of this vulnerability requires an authenticated attacker who possesses low privilege credentials to access the affected Cisco device. The attacker must craft a specific URL that, when processed by the vulnerable web UI, triggers a critical system failure. This crafted HTTP request exploits the improper input validation by sending malformed or specially constructed URL parameters that the system cannot properly handle. The vulnerability operates at the application layer and specifically targets the web interface component of the IOS software stack, making it particularly concerning for network administrators who rely on web-based management interfaces for device configuration and monitoring.
The operational impact of this vulnerability extends beyond simple service disruption, as it can result in complete system unavailability for legitimate users. When successfully exploited, the affected device undergoes an automatic reload process that temporarily removes it from network operations. This denial of service condition can have cascading effects on network infrastructure, potentially disrupting critical services that depend on the availability of the affected device. Network administrators may experience extended downtime while the device restarts and re-establishes connections, potentially affecting network performance and availability for other connected systems.
Organizations should implement immediate mitigations including applying the latest security patches from Cisco that address the input validation flaws in the web UI component. Network segmentation and access control measures should be enhanced to limit the attack surface by restricting access to the web interface to only authorized personnel with legitimate business needs. Monitoring systems should be configured to detect unusual patterns in web interface access attempts, particularly those involving malformed URL requests that could indicate exploitation attempts. The vulnerability aligns with CWE-20, which specifically addresses "Improper Input Validation" and falls under the ATT&CK technique T1499.004 for "Network Denial of Service" where adversaries leverage system weaknesses to disrupt network services. Security teams should also consider implementing web application firewalls to filter malicious HTTP requests before they reach the vulnerable web UI component, while maintaining regular security audits to identify and remediate similar input validation issues across other network management interfaces.