CVE-2025-6638Network attack vector

Service interruption via greedy language-code regex

Published Sep 12, 2025 · Updated Sep 12, 2025

Regular expression denial of service in Hugging Face Transformers before 4.53.0 allows remote attackers to exhaust CPU via crafted text. MarianTokenizer.remove_language_code applies the unbounded greedy pattern >>.+<< through both match and substitution, causing excessive regex work on malformed prefixes. Exposure requires an application to pass attacker-controlled text to a Marian tokenizer; successful requests monopolize CPU and interrupt that application's service.

CVSS severity5.3
Medium
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Hugging Face Transformers before 4.53.0 allows remote attackers to exhaust CPU via crafted text. MarianTokenizer.remove_language_code applies the unbounded greedy pattern >>.+<< through both match and substitution, causing excessive regex work on malformed prefixes. Exposure requires an application to pass attacker-controlled text to a Marian tokenizer; successful requests monopolize CPU and interrupt that application's service.

The record

CVE
CVE-2025-6638
Published
Sep 12, 2025
Updated
Sep 12, 2025
Vendor
Hugging Face
Product
Hugging Face Transformers
Classifications
CWE-1333, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 12, 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=unspecified <4.53.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hugging Face · Hugging Face Transformersversion=unspecified <4.53.0

Published CVSS scores

5.3GitHub Advisory DatabaseCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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