Authenticated server crash via invalid regex fallback
Published May 30, 2025 · Updated May 30, 2025
Denial of service in vLLM 0.8.0 through 0.8.5.post1 allows remote authenticated users to crash its server via an invalid structured-output regex. When xgrammar rejects the regex under the auto backend, the server assumes an unsupported schema, falls back to guidance without another validation check, and lets the resulting exception terminate the engine. A client needs API access and structured output must be requested; the demonstrated consequence is a server crash, not data access or modification.
Summary
What happened
Denial of service in vLLM 0.8.0 through 0.8.5.post1 allows remote authenticated users to crash its server via an invalid structured-output regex. When xgrammar rejects the regex under the auto backend, the server assumes an unsupported schema, falls back to guidance without another validation check, and lets the resulting exception terminate the engine. A client needs API access and structured output must be requested; the demonstrated consequence is a server crash, not data access or modification.
The record
- CVE
- CVE-2025-48943
- Published
- May 30, 2025
- Updated
- May 30, 2025
- Vendor
- vLLM Project
- Product
- vLLM
- Classifications
- T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 30, 2025CVE publishedPublication date reported by the CVE source.
- May 30, 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.
- Affected versionversion=>= 0.8.0, < 0.9.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Invalid guided-regex crash reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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