CVE-2026-114458 in mod_qos
Summary
by MITRE • 10/22/2026
A flaw was found in mod_qos. An unauthenticated remote attacker can cause a Denial of Service (DoS) by maintaining numerous concurrent low-rate connections to a target server. When connection rate monitoring is active, the module fails to verify array boundaries when recording client IP addresses, allowing more connection records to be added than the allocated buffer can hold. This issue leads to heap memory corruption, which can crash the web server process.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified in mod_qos represents a critical security flaw within an Apache HTTP Server module designed for quality of service management and traffic control. The core technical deficiency lies in how the module handles connection rate monitoring when it is actively enabled on the target system. Specifically, the software fails to perform proper array boundary verification while recording client IP addresses associated with incoming connections. This lack of input validation allows an unauthenticated remote attacker to exploit the logic error by maintaining a large number of concurrent low-rate connections against the targeted server. Because the module does not check if the internal data structures have reached their capacity limits before writing new entries, it permits more connection records to be added than the allocated buffer can securely hold.
This boundary violation results in heap memory corruption as the application writes data beyond the intended memory boundaries of its internal arrays. The immediate operational impact of this flaw is a denial of service condition affecting the web server process itself. When the heap corruption occurs, it typically leads to an abrupt crash or termination of the Apache HTTP Server process hosting mod_qos. This disruption effectively renders the associated website or application unavailable to legitimate users until the service is manually restarted by system administrators. The vulnerability does not require authentication, making it particularly dangerous as any external actor on the network can trigger this state without needing valid credentials or prior access privileges.
From a classification perspective, this issue aligns with CWE-120, which describes buffer copy without checking size limits, and more specifically relates to improper input validation leading to memory corruption. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability facilitates Denial of Service attacks by compromising the availability component of the CIA triad. The attack vector is remote and network-based, allowing adversaries to disrupt service continuity with minimal effort once they identify a server running an affected version of mod_qos with rate monitoring enabled.
Mitigation strategies should prioritize immediate patching if available from the vendor or upstream maintainers. In cases where updating software is not immediately feasible, administrators can mitigate the risk by disabling connection rate monitoring features within mod_qos configuration files if those specific functionalities are not strictly required for their operational environment. Additionally, implementing network-level controls such as Web Application Firewalls or intrusion prevention systems that limit the number of concurrent connections from a single IP address can help reduce the likelihood of triggering this vulnerability. Regular security audits and code reviews focusing on memory management practices in third-party modules are also recommended to prevent similar buffer overflow issues in future deployments.