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HIGH7.5

PYSEC-2026-1445

H2O Vulnerable to Denial of Service (DoS) via `/3/Parse` Endpoint

Details

A vulnerability in the `/3/Parse` endpoint of h2oai/h2o-3 version 3.46.0.1 allows for a denial of service (DoS) attack. The endpoint uses a user-specified string to construct a regular expression, which is then applied to another user-specified string. By sending multiple simultaneous requests, an attacker can exhaust all available threads, leading to a complete denial of service.

Are you affected?

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Affected packages

PyPI/h2o
Introduced in: 3.30.0.7

No fixed version published yet for h2o (pip). Pin to a known-safe version or switch to an alternative.

References