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GHSA-389x-67px-mjg3

MediumCVSS 6.5 / 10
Published Apr 9, 2025·Last modified Feb 4, 2026
Affected Components(0)

No affected components available

Description

Summary

Xgrammar includes a cache for compiled grammars to increase performance with repeated use of the same grammar. This cache is held in memory. Since the cache is unbounded, a system making use of xgrammar can be abused to fill up a host's memory and case a denial of service. For example, sending many small requests to an LLM inference server with unique JSON schemas would eventually cause this denial of service to occur.

Details

The fix is to add a limit to the cache size. This was done in https://github.com/mlc-ai/xgrammar/pull/243

An example of making use of the new cache size limit can be found in vLLM here: https://github.com/vllm-project/vllm/pull/16283

Impact

Any system making use of Xgrammar and taking requests as input from potentially untrusted parties would be vulnerable to this denial of service issue.

Risk Scores
Base Score
6.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.47%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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