CloakBrowser cloakserve Unauthenticated Path Traversal Leading to Arbitrary Directory Deletion (CVE-2026-45727)

CloakBrowser’s cloakserve component is vulnerable to an unauthenticated path traversal attack. The vulnerability stems from the direct use of the user-supplied fingerprint query parameter as a filesystem path component when creating Chrome profile directories. An attacker, without needing authentication, can send a crafted fingerprint value containing path traversal sequences to manipulate the user_data_dir resolution to point outside the intended data_dir. This vulnerability affects CloakBrowser versions 0.3.27 and earlier. The default configuration of cloakserve binding to 0.0.0.0 exacerbates the issue by making it network-exposed. By exploiting this vulnerability, attackers can delete arbitrary directories accessible to the service user when Chrome fails to start or during process cleanup.

Attack Chain

1. The attacker sends an HTTP request to the exposed cloakserve port.
2. The request includes a crafted fingerprint query parameter containing path traversal sequences (e.g., ../).
3. cloakserve uses the fingerprint parameter to construct a path for the Chrome profile directory (user_data_dir).
4. The path traversal sequences in the fingerprint parameter cause user_data_dir to resolve outside the configured data_dir.
5. Chrome attempts to start using the manipulated user_data_dir.
6. Chrome fails to start, potentially due to issues with the traversed path or profile directory.
7. During cleanup or when the process is terminated, shutil.rmtree() is called to delete the user_data_dir.
8. Due to the path traversal, shutil.rmtree() deletes an arbitrary directory accessible to the service user.

Impact

Successful exploitation allows an unauthenticated attacker with network access to the cloakserve port to delete arbitrary directories accessible to the service user. The number of affected installations is unknown. This vulnerability allows for denial of service or potentially more severe impacts depending on the contents and permissions of the deleted directories.

Recommendation

• Upgrade CloakBrowser to version 0.3.28 or later to remediate the vulnerability as advised in the overview.
• Restrict network access to the cloakserve port (typically port 8080) as described in the mitigations section of the linked advisory.
• Deploy the Sigma rule “Detect CloakBrowser Path Traversal Attempt via Crafted Fingerprint” to monitor for suspicious fingerprint parameters containing path traversal sequences.