CVE-2026-48834 in Answer
Summary
by MITRE • 08/05/2026
Improper Handling of Length Parameter Inconsistency vulnerability in Apache Answer.
This issue affects Apache Answer: through 2.0.1.
Unauthenticated attackers can cause a denial of service via a specially crafted Accept-Language header that triggers excessive CPU consumption during parsing. Users are recommended to upgrade to version 2.0.2, which fixes the issue.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability in Apache Answer represents a critical improper handling of length parameter inconsistency that exposes the application to denial of service attacks through crafted HTTP headers. This weakness specifically manifests when processing the Accept-Language header parameter, where the application fails to properly validate or constrain the length of input data during parsing operations. The flaw exists within the web application's request handling mechanism and demonstrates a classic example of insufficient input validation that can be exploited by unauthenticated attackers without requiring any privileged access or credentials. The vulnerability affects all versions through 2.0.1, indicating it has been present in the codebase for an extended period and represents a significant security oversight in the application's architecture.
The technical execution of this attack involves crafting a specially formatted Accept-Language header that contains an excessively long parameter value, which triggers inefficient parsing logic within Apache Answer's processing pipeline. During the parsing operation, the application consumes disproportionate CPU resources as it attempts to handle the malformed input, leading to excessive resource consumption that can overwhelm the server's processing capabilities. This behavior creates a denial of service condition where legitimate users may experience degraded service or complete unavailability of the application. The vulnerability operates at the HTTP request level and demonstrates how seemingly benign header parameters can be weaponized to create system-wide impact through resource exhaustion attacks.
From an operational perspective, this vulnerability presents a significant risk to Apache Answer deployments as it allows attackers to consume system resources without requiring authentication or specialized privileges. The attack vector is particularly dangerous because it leverages standard HTTP headers that are commonly sent by web browsers and clients, making detection more challenging for security monitoring systems. The impact extends beyond simple service disruption as the excessive CPU consumption can affect other applications running on the same server infrastructure, potentially causing cascading failures throughout the hosting environment. Organizations using affected versions should immediately implement mitigation strategies while planning for the mandatory upgrade to version 2.0.2.
The vulnerability aligns with CWE-129 and CWE-770 categories from the Common Weakness Enumeration database, specifically addressing improper validation of input length parameters and insufficient resource management during parsing operations. From an ATT&CK framework perspective, this represents a denial of service technique that can be categorized under T1499.004 - Endpoint Denial of Service, where attackers exploit application-level vulnerabilities to consume system resources. The weakness demonstrates poor defensive programming practices and inadequate input sanitization controls that are fundamental requirements for secure web application development. Organizations should consider implementing rate limiting and input validation mechanisms at the network level as temporary mitigations while upgrading to the patched version that addresses the root cause of the parsing inconsistency.
The remediation approach focuses on upgrading to Apache Answer version 2.0.2 which contains the necessary code modifications to properly validate length parameters in Accept-Language headers. This upgrade ensures that the application implements appropriate bounds checking and resource management during header parsing operations, preventing the excessive CPU consumption that previously occurred with malformed inputs. System administrators should also consider implementing additional security controls such as WAF rules that can detect and block suspicious header patterns, along with monitoring configurations that alert on unusual CPU usage patterns that may indicate exploitation attempts.