CVE-2025-57809Public exploitNetwork attack vector

Service crash via unbounded grammar recursion

Published Aug 25, 2025 · Updated Aug 26, 2025

Uncontrolled recursion in MLC XGrammar before 0.1.21 allows remote attackers to crash consuming applications via crafted grammars. GrammarMatcherBase::ExpandEquivalentStackElements recursively expands self-referential grammar states until the process exhausts its call stack and receives SIGSEGV. Reachability requires a consuming tool to accept attacker-supplied grammars; the resulting process crash interrupts that tool's service.

CVSS severity7.5
High
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled recursion in MLC XGrammar before 0.1.21 allows remote attackers to crash consuming applications via crafted grammars. GrammarMatcherBase::ExpandEquivalentStackElements recursively expands self-referential grammar states until the process exhausts its call stack and receives SIGSEGV. Reachability requires a consuming tool to accept attacker-supplied grammars; the resulting process crash interrupts that tool's service.

The record

CVE
CVE-2025-57809
Published
Aug 25, 2025
Updated
Aug 26, 2025
Vendor
MLC
Product
XGrammar
Classifications
CWE-674, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 26, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.1.21

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MLC · XGrammarversion=< 0.1.21

Published CVSS scores

7.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-674Uncontrolled Recursion
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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