CVE-2026-77815: Improper Link Resolution Before File Access ('Link Following') in zanllp infinite-image-browsing
Description
to_abs_path in scripts/iib/tool.py normalised the requested path with os.path.normpath, which collapses dot segments but does not resolve symbolic links. A symlink placed inside a scanned directory therefore satisfies the containment comparison performed by is_path_trusted in scripts/iib/api.py while pointing outside that directory, and FileResponse follows the link when serving the response, so a link created in an image directory and targeting a file such as /etc/passwd discloses that file. Whether the check applies depends on get_enable_access_control in scripts/iib/tool.py: it returns true when IIB_ACCESS_CONTROL is set to enable, false when set to disable, and otherwise true when the host Stable Diffusion WebUI was started with share, ngrok, listen or server_name, falling back to false. Confinement is therefore active in the network-exposed WebUI deployments that rely on it, while a standalone run with no such option serves every readable file regardless of this flaw. The fix resolves the path with os.path.realpath.
CVSS v4.0
Score 8.7high
Affected software
zanllp
infinite-image-browsing
pkg:github/infinite-image-browsingRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in zanllp infinite-image-browsing stems from the to_abs_path function using os.path.normpath to normalize requested paths, which collapses dot segments but does not resolve symbolic links. This allows a symlink inside a scanned directory to pass containment checks and point outside the directory. When FileResponse serves the file, it follows the symlink, disclosing files like /etc/passwd. Access control enforcement depends on the get_enable_access_control function, which returns true or false based on environment variables and startup options. The fix involves using os.path.realpath to fully resolve symbolic links before access checks.
Potential Impact
An attacker can exploit this vulnerability to read arbitrary files on the server by creating symbolic links inside image directories that point to sensitive files outside those directories. This leads to unauthorized disclosure of potentially sensitive system files. The impact is mitigated in network-exposed deployments with access control enabled, but standalone runs without these protections are fully vulnerable.
Mitigation Recommendations
A fix is available that resolves the path using os.path.realpath to properly handle symbolic links before access checks. Users should update to a version including this fix. Access control settings should be reviewed to ensure confinement is enabled, especially for standalone deployments. No additional mitigation is required if the fix is applied.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-21T14:14:43.821Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a8869e8acd9273b494e4713
Added to database: 08/21/2026, 15:08:24 UTC
Last enriched: 09/25/2026, 02:42:25 UTC
Last updated: 10/05/2026, 18:48:22 UTC
Views: 57
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