Workspace Bypass in Hermes WebUI Allows Local File Access

Executive Summary

CVE-2026-49957 is a workspace boundary bypass vulnerability in Hermes WebUI versions before 0.51.269. It allows authenticated attackers to circumvent blocked-root path checks by exploiting an early return in the SSH/remote terminal profile workspace resolution logic within the function _remote_terminal_workspace_candidate().

Attackers can configure a remote terminal working directory to a system directory such as /etc. Because the workspace resolution path accepts this directory as a trusted local workspace root before the blocked-root guard executes, attackers can gain read access to local system files through workspace file-read helpers.

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Impact Analysis

This vulnerability can allow authenticated attackers to read sensitive local system files by tricking the Hermes WebUI into treating blocked system directories like /etc as trusted local workspaces.

Such unauthorized read access could expose critical configuration files (e.g., /etc/hosts), potentially leading to information disclosure and aiding further attacks.

The vulnerability has a CVSS v3.1 base score of 7.7, indicating a high severity impact on confidentiality without affecting integrity or availability.

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Detection Guidance

This vulnerability involves the acceptance of blocked system root directories such as /etc as remote terminal workspace roots due to an early return in the workspace resolution logic. Detection involves checking if any remote terminal profiles or SSH configurations have their working directory (terminal.cwd) set to sensitive system directories like /etc.

You can inspect the configuration files or profiles used by Hermes WebUI to identify if any remote terminal workspace is configured with a working directory pointing to blocked system paths.

Suggested commands to detect potentially vulnerable configurations include searching for workspace or terminal profile settings referencing system directories:

• grep -r 'terminal.cwd' /path/to/hermes/configs | grep '/etc'
• grep -r 'workspace' /path/to/hermes/configs | grep '/etc'

Additionally, monitoring file-read helper logs or access logs for unexpected reads from system directories like /etc may help detect exploitation attempts.

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Mitigation Strategies

The primary mitigation step is to update Hermes WebUI to version 0.51.269 or later, where the vulnerability has been fixed by adding blocked-root guard checks to reject system directories like /etc as remote terminal workspace roots.

If immediate updating is not possible, review and modify remote terminal workspace configurations to ensure that no workspace or terminal profile uses system directories such as /etc as the working directory.

Additionally, consider auditing and restricting authenticated users' ability to configure remote terminal workspaces to prevent setting blocked root paths.

Be aware that some fallback functions may still allow unvalidated blocked paths, so applying the official patch is strongly recommended to fully mitigate the risk.

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Compliance Impact

CVE-2026-49957 allows authenticated attackers to bypass workspace path restrictions and gain read access to sensitive local system files by exploiting a vulnerability in the Hermes WebUI workspace resolution logic.

This unauthorized access to system files could lead to exposure of sensitive information, which may impact compliance with data protection standards and regulations such as GDPR and HIPAA that require strict controls on access to sensitive data.

By enabling attackers to read protected system files, the vulnerability increases the risk of data breaches or unauthorized disclosure of personal or protected health information, potentially violating regulatory requirements for confidentiality and data security.

Therefore, organizations using affected versions of Hermes WebUI should update to the patched version to mitigate this risk and maintain compliance with relevant security and privacy standards.

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