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HIGH7.5

PYSEC-2026-1440

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

Details

A vulnerability in the `/3/ParseSetup` endpoint of h2oai/h2o-3 version 3.46.0.1 allows for a denial of service (DoS) attack. The endpoint applies a user-specified regular expression to a user-controllable string. This can be exploited by an attacker to cause inefficient regular expression complexity, leading to the exhaustion of server resources and making the server unresponsive.

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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