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GHSA-4j5m-wc25-pvh7

MediumCVSS 4.4 / 10
Published May 21, 2026·Last modified May 21, 2026
Affected Components(0)

No affected components available

Description

Impact

A maliciously crafted .onetoc2 table-of-contents file can cause Parser::parse_notebook to open arbitrary files on the host filesystem outside the notebook's directory. The parser reads entry names listed inside the .onetoc2 and joins them against the notebook's base directory without validating that they are relative paths confined to that directory.

The parser will bail out when the target file fails to parse as a OneNote section, so direct content exfiltration through the parser's return value is not practical, though file-existence probing and denial-of-service via large or special files remain possible.

Anyone using onenote_parser to parse .onetoc2 files received from untrusted sources is affected. Users who only ever parse their own notebooks are not at meaningful risk.

Patches

Fixed in onenote_parser 1.1.1. The fix rejects absolute paths, parent-directory components, and other invalid path characters in entry names, and additionally canonicalises the resolved path to confirm it stays inside the notebook's base directory.

Workarounds

For users who cannot upgrade to 1.1.1:

  • Only call Parser::parse_notebook on .onetoc2 files from trusted sources.
  • Alternatively, use Parser::parse_section / Parser::parse_section_buffer on individual .one files, which do not perform the directory walk.
Risk Scores
Base Score
4.4

The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the availability of the system.

Threat Intelligence
4.1

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.14%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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