PT-2026-53439 · Pypi · H2O

Published 2026-06-29 · Updated 2026-06-29

OSV

CVSS v3.1

9.3

Critical

Base vector

AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H

Remote unauthenticated attackers can overwrite arbitrary server files with attacker-controllable data. The data that the attacker can control is not entirely arbitrary. h2o writes a CSV/XLS/etc file to disk, so the attacker data is wrapped in quotations and starts with "C1", if they're exporting as CSV.

Fix

Related Identifiers

PYSEC-2026-350

Affected Products

H2O

References · 7

• https://osv.dev/vulnerability/PYSEC-2026-350 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2023-6569 · Security Note
• https://github.com/h2oai/h2o-3/commit/e8884f5187eb81311877c5f0dd4d6d9c70f33d78 · Note
• https://github.com/h2oai/h2o-3 · Note
• https://pypi.org/project/h2o · Note
• https://github.com/advisories/GHSA-gqrq-j6pm-98c2 · Note
• https://huntr.com/bounties/a5d003dc-c23e-4c98-8dcf-35ba9252fa3c · Note