CVE-2024-5986

published 2026-02-02

CVE-2024-5986: 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…

Priority P2 65 critical 9.1 CVSS 3.0

AV N AC L PR N UI N S U C N I H A H

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.

Affected

2 ranges

Vendor	Product	Version range	Fixed in
h2o	h2o	0 – 3.46.0.1	—
h2oai	h2oai_h2o-3	unspecified – latest	—

Detection & IOCs extracted from sources · hover to see the quote

url /3/Parse↗

url /3/Frames/framename/export↗

• → Monitor HTTP requests to the /3/Parse endpoint for attacker-controlled header injection into empty files, which is the first stage of the exploit chain. ↗
• → Monitor HTTP requests to the /3/Frames/framename/export endpoint for attempts to export frames to sensitive filesystem paths (e.g., SSH keys, script files), which is the second stage of the exploit chain enabling arbitrary file write. ↗
• → Alert on any h2o-3 process writing to sensitive paths (e.g., ~/.ssh/, cron directories, shell scripts) as this indicates successful exploitation of the arbitrary file write primitive. ↗

• · The vulnerability affects h2o-3 version 3.46.0.1 specifically; confirm the deployed version before applying detections. ↗
• · Both the /3/Parse and /3/Frames/framename/export endpoints must be accessible to remote attackers for the full exploit chain to succeed; restricting network access to these endpoints reduces exposure. ↗
• · No fix was available as of the published date (Feb 03, 2026) for both Maven and pip distributions of h2o. ↗

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