CVE-2026-25039
Received Received - Intake

UNC Path Handling Flaw in Parsec File Sharing

Publication date: 2026-07-20

Last updated on: 2026-07-20

Assigner: GitHub, Inc.

Description
Parsec is a cloud-based application for simple and cryptographically secure file sharing. The application does not sanitize the workspace name, creating a vulnerability if that workspace name is a UNC path. When creating mountpoint in the windows filesystem to mount the workspace of an organization, the application does not sanitize the workspace name. The cause issue if the workspace name evaluate to a UNC path since it's allowed for the name to containt `\` char. If the UNC path is invalid (or the targeted resource is not available) the application become unresponsive otherwise the system will interact with the mounted UNC path allowing the attacker to retrieve to [`NTLM`] hash.

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Meta Information

Published
2026-07-20
Last Modified
2026-07-20
Generated
2026-07-21
AI Q&A
2026-07-20
EPSS Evaluated
N/A
NVD
CVE-2026-25039
EUVD
EUVD-2026-45968

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
scille parsec-cloud to 3.3.3-rc.0 (exc)
scille libparsec_mountpoint to 3.3.3-rc.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-40 The product accepts input that identifies a Windows UNC share ('\\UNC\share\name') that potentially redirects access to an unintended location or arbitrary file.

Attack-Flow Graph

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Executive Summary

This vulnerability in Parsec involves improper sanitization of workspace names, allowing attackers to use backslashes to create UNC paths. If a workspace name is crafted as a UNC path (e.g., \\192.168.1.3\test), the application may mount it, enabling attackers to intercept NTLM hashes or cause the application to hang if the path is invalid.

Detection Guidance

Check for unusual UNC path usage in workspace names by inspecting Parsec application logs or network traffic for connections to unexpected SMB shares. Monitor for unresponsive Parsec instances when accessing workspaces with backslashes in names.

Impact Analysis

An attacker could trick you into accessing a malicious workspace, leading to NTLM hash theft or application unresponsiveness. This could compromise your system's security or disrupt Parsec's functionality.

Compliance Impact

This vulnerability could lead to unauthorized access or data exfiltration, violating confidentiality requirements in GDPR and HIPAA. Organizations using affected versions may face compliance risks due to potential breaches.

Mitigation Strategies

Update Parsec to version 3.3.3-rc.0 or later. Disable workspace sharing with untrusted users until patched. Block outbound SMB traffic (TCP 445) if not required. Review workspace names for backslashes or UNC patterns.

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