CVE-2026-25048 is a vulnerability identified in the mlc-ai xgrammar library, an open-source tool designed for efficient, flexible, and portable structured generation. The root cause is uncontrolled recursion triggered by multi-level nested syntax constructs in versions prior to 0.1.32. This uncontrolled recursion leads to a segmentation fault, causing the application to crash and dump core, effectively resulting in a denial-of-service (DoS) condition. The vulnerability is classified under CWE-674, which pertains to uncontrolled recursion issues that can exhaust stack memory. The CVSS 4.0 vector indicates that the attack vector is network-based (AV:N), requires no privileges (PR:N), no user interaction (UI:N), and no authentication (AT:N), making it remotely exploitable. The impact is primarily on availability (VA:H), with no confidentiality or integrity impact. The vulnerability was reserved in January 2026 and published in March 2026, with a patch released in version 0.1.32 of xgrammar. No known exploits have been reported in the wild, but the ease of triggering the fault makes it a significant risk for affected systems. The vulnerability affects any software or service that integrates the vulnerable xgrammar versions, especially those processing complex nested syntax structures in AI or language generation contexts.

The primary impact of CVE-2026-25048 is a denial-of-service condition caused by application crashes due to segmentation faults. Organizations using vulnerable versions of xgrammar in AI, natural language processing, or structured generation applications may experience service outages, degraded performance, or system instability. This can disrupt business operations, especially in environments relying on automated language generation or AI-driven workflows. Since the vulnerability can be exploited remotely without authentication or user interaction, attackers can cause widespread disruption with minimal effort. The lack of confidentiality or integrity impact limits data breach risks, but availability loss can affect customer trust, operational continuity, and potentially lead to financial losses. Industries heavily dependent on AI tooling, such as technology companies, research institutions, and cloud service providers, face higher operational risks. Additionally, embedded or integrated systems using xgrammar may become unstable, complicating incident response and recovery.

To mitigate CVE-2026-25048, organizations should immediately upgrade all instances of the mlc-ai xgrammar library to version 0.1.32 or later, where the uncontrolled recursion issue has been patched. Developers should audit their codebases and dependencies to identify any use of vulnerable xgrammar versions, including transitive dependencies in AI or language processing pipelines. Implement input validation and limit the depth of nested syntax structures where feasible to reduce the risk of triggering recursion faults. Employ runtime monitoring and anomaly detection to identify unusual crashes or segmentation faults related to xgrammar usage. In environments where immediate upgrading is not possible, consider isolating or sandboxing applications using xgrammar to contain potential crashes and prevent cascading failures. Maintain up-to-date backups and incident response plans to quickly recover from denial-of-service incidents. Finally, track vendor advisories and community updates for any emerging exploit information or additional patches.