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CVE-2025-2099: Regular Expression Denial of Service (ReDoS) in huggingface/transformers

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-05-19 · updated 2026-06-17
• Weakness: CWE-1333

Description

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.

Affected products

• huggingface/transformers: through 4.48.3

References

• https://github.com/huggingface/transformers/commit/8cb522b4190bd556ce51be04942720650b1a3e57
• https://huntr.com/bounties/97b780f3-ffca-424f-ad5d-0e1c57a5bde4

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