A vulnerability in the URLValidator feature of Apache Struts could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected system.
The vulnerability is due to insufficient validation of user-supplied input when the affected software uses the URLValidator feature to validate URLs. An attacker could exploit this vulnerability by submitting a crafted URL in a form field of an application utilizing an affected version of Apache Struts. An exploit could trigger a condition in the regular expression (regex) processing by the URLValidator that would consume excessive amounts of CPU resources, resulting in a DoS condition.
The Apache Software Foundation has confirmed the vulnerability and releases software updates.
To exploit this vulnerability, an attacker would need to supply a crafted URL to a form field of an application utilizing the affected software on a targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.
A successful exploit requires the use of the URLValidator feature of the affected software.
This vulnerability is related to an incomplete fix for CVE-2017-7672, which is documented in The Apache Software Foundation's security bulletin at the following link: S2-047
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
The Apache Software Foundation has released a security bulletin at the following link: S2-050
The Apache Software Foundation has released software updates at the following link: Struts 2.5.13
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.