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CVE-2025-2099

Regular Expression Denial of Service (ReDoS) in huggingface/transformers

5.3 MediumFix available

CVE-2025-2099 is a medium vulnerability (CVSS 5.3) in Huggingface Huggingface/transformers, published May 19, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.61%, the 49th percentile. Fixed in transformers 4.50.0.

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.61%Up 0.6 points since May 19, 2025
90%50%10%1%

What each source reports

CVE List Score used 5.3

Regular Expression Denial of Service (ReDoS) in huggingface/transformers

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Record
CVE-2025-2099
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-1333
Updated
2026-11-02
EUVDEUVD-2025-15691 5.3

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Record
EUVD-2025-15691
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-qq3j-4f4f-9583 5.3

Hugging Face Transformers Regular Expression Denial of Service

A Regular Expression Denial of Service (ReDoS) exists in the preprocess_string() function of the transformers.testing_utils module. In versions before 4.50.0, the regex used to process code blocks in docstrings contains nested quantifiers that can trigger catastrophic backtracking when given inputs with many newline characters. An attacker who can supply such input to preprocess_string() (or code paths that call it) can force excessive CPU usage and degrade availability.

Fix: released in 4.50.0, which rewrites the regex to avoid the inefficient pattern. ([GitHub][1])

  • Affected: < 4.50.0
  • Patched: 4.50.0
Record
GHSA-qq3j-4f4f-9583
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-1333
Updated
2026-11-02
NVD 7.5

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Record
CVE-2025-2099
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-1333
Updated
2026-11-02
OSV 5.3

Regular Expression Denial of Service (ReDoS) in huggingface/transformers

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Record
CVE-2025-2099
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-1333
Updated
2026-11-02
OSVGHSA-qq3j-4f4f-9583 5.3

Hugging Face Transformers Regular Expression Denial of Service

A Regular Expression Denial of Service (ReDoS) exists in the preprocess_string() function of the transformers.testing_utils module. In versions before 4.50.0, the regex used to process code blocks in docstrings contains nested quantifiers that can trigger catastrophic backtracking when given inputs with many newline characters. An attacker who can supply such input to preprocess_string() (or code paths that call it) can force excessive CPU usage and degrade availability.

Fix: released in 4.50.0, which rewrites the regex to avoid the inefficient pattern. ([GitHub][1])

  • Affected: < 4.50.0
  • Patched: 4.50.0
Record
GHSA-qq3j-4f4f-9583
CVSS 3.0
5.3 MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness
CWE-1333
Updated
2026-11-02
OSVPYSEC-2025-40 7.5

A vulnerability in the preprocess_string() function of the transformers.testing_utils module in huggingface/transformers version v4.48.3 allows for a Regular Expression Denial of Service (ReDoS) attack. The regular expression used to process code blocks in docstrings contains nested quantifiers, leading to exponential backtracking when processing input with a large number of newline characters. An attacker can exploit this by providing a specially crafted payload, causing high CPU usage and potential application downtime, effectively resulting in a Denial of Service (DoS) scenario.

Record
PYSEC-2025-40
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
transformers
PyPI
before 4.50.0
4.50.0
transformers
PyPI
before 4.50.0, plus listed versions
0.12.0.02.1.02.1.12.10.0
Show 45 moreShow less
2.11.02.2.02.2.12.2.22.3.02.4.02.4.12.5.02.5.12.6.02.7.02.8.02.9.02.9.13.0.03.0.13.0.23.1.03.2.03.3.03.3.13.4.03.5.03.5.14.0.04.0.0rc14.0.14.1.04.1.14.10.04.10.14.10.24.10.34.11.04.11.14.11.24.11.34.12.04.12.14.12.24.12.34.12.44.12.54.13.04.14.0
4.50.0
transformers
PyPI
before 4.49.0, plus listed versions
0.12.0.02.1.02.1.12.10.0
Show 45 moreShow less
2.11.02.2.02.2.12.2.22.3.02.4.02.4.12.5.02.5.12.6.02.7.02.8.02.9.02.9.13.0.03.0.13.0.23.1.03.2.03.3.03.3.13.4.03.5.03.5.14.0.04.0.0rc14.0.14.1.04.1.14.10.04.10.14.10.24.10.34.11.04.11.14.11.24.11.34.12.04.12.14.12.24.12.34.12.44.12.54.13.04.14.0
4.49.0

History

History
WhenChangedSources
2026-11-02createdCVE List, EUVD, GitHub Advisories, NVD, OSV

References

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Left out here: 304 versions. The JSON record has them.

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