CVE-2025-6703 in neqo
Summary
by MITRE • 06/26/2025
Improper Input Validation vulnerability in Mozilla neqo leads to an unexploitable crash..This issue affects neqo: from 0.4.24 through 0.13.2.
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Analysis
by VulDB Data Team • 12/03/2025
The vulnerability identified as CVE-2025-6703 represents an improper input validation flaw within Mozilla's neqo library, a critical component of the network stack used for QUIC protocol implementation. This library serves as the foundation for secure web communications and is integrated into various Mozilla products including Firefox and other applications that rely on QUIC for enhanced network performance. The vulnerability specifically manifests in versions ranging from 0.4.24 through 0.13.2, indicating a substantial release range that could potentially affect numerous applications and systems utilizing this networking component.
The technical nature of this flaw stems from insufficient validation of input parameters received by the neqo library during QUIC protocol processing. When malformed or unexpected input data is processed by the library, it fails to properly validate the incoming data structures, leading to an unexploitable crash condition. This crash occurs during the normal processing flow of QUIC packets, where the library attempts to parse and handle incoming network data without adequate safeguards against malformed input. The vulnerability operates at the protocol implementation level, making it particularly concerning as it can be triggered through network-based attacks that send specially crafted QUIC packets to vulnerable systems.
From an operational impact perspective, while the vulnerability is classified as unexploitable in terms of allowing remote code execution or privilege escalation, the crash condition presents significant security implications for system availability and stability. The uncontrolled crash can lead to denial of service conditions where applications relying on neqo for network communication may experience unexpected termination or system instability. This is particularly problematic for applications that depend on continuous network connectivity and cannot tolerate unexpected service interruptions. The vulnerability affects the broader QUIC ecosystem and could potentially be leveraged in combination with other exploits to create more sophisticated attack vectors.
Security practitioners should note that this vulnerability aligns with CWE-20, Improper Input Validation, which is a fundamental weakness in software design that allows malicious inputs to cause unexpected behavior in applications. The ATT&CK framework categorizes this type of vulnerability under T1210, Exploitation of Remote Services, as it represents a potential attack surface that can be exploited through network-based inputs. Organizations utilizing affected versions of neqo should prioritize immediate patching and updates to prevent potential exploitation scenarios. The vulnerability demonstrates the critical importance of input validation in network libraries and highlights the need for comprehensive security testing of protocol implementations. Mitigation strategies should include upgrading to patched versions of the neqo library, implementing network monitoring to detect suspicious QUIC traffic patterns, and maintaining robust incident response procedures for handling potential crash conditions that could affect system availability.