CVE-2026-49958: Hermes WebUI < 0.51.303 TOCTOU Race Condition via git_discard

Vulnerability summary

CVE-2026-49958 is a medium (CVSS 5.0) vulnerability in nesquena hermes-webui. EPSS estimates a 0.10% chance of exploitation in the next 30 days, higher than 1% of scored vulnerabilities.

Timeline

1. 09-06-2026
   PublishedVulnerability first disclosed.
2. 14-07-2026
   Last modifiedVulnerability information updated.

Description

Hermes WebUI before version 0.51.303 contains a time-of-check time-of-use (TOCTOU) race condition vulnerability in the git_discard function within api/workspace_git.py that allows attackers to delete files outside the configured workspace boundary by replacing a validated path component with a symlink after validation but before deletion. Attackers can substitute a workspace-controlled path component with a symlink pointing to an external directory between the safe_resolve_ws() validation step and the subsequent Path.unlink() or shutil.rmtree() deletion call, causing the delete operation to follow the symlink and remove arbitrary files outside the workspace.

• CWE-367Time-of-check Time-of-use (TOCTOU) Race ConditionThe product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.