CRITICAL 9.1
PYSEC-2026-353
H2O has an External Control of File Name or Path vulnerability
Details
A vulnerability in h2oai/h2o-3 version 3.46.0.1 allows remote attackers to write arbitrary data to any file on the server. This is achieved by exploiting the `/3/Parse` endpoint to inject attacker-controlled data as the header of an empty file, which is then exported using the `/3/Frames/framename/export` endpoint. The impact of this vulnerability includes the potential for remote code execution and complete access to the system running h2o-3, as attackers can overwrite critical files such as private SSH keys or script files.
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Affected packages
PyPI / h2o
Introduced in:
0 No fixed version published yet for h2o (pip). Pin to a known-safe version or switch to an alternative.