CVE-2025-59159: 
JavaScript vulnerability analysis and mitigation

CVE-2025-59159 affects SillyTavern, a locally installed user interface for interacting with text generation large language models, image generation engines, and text-to-speech voice models. The vulnerability, discovered in versions prior to 1.13.4, allows attackers to perform DNS rebinding attacks against the web interface, enabling unauthorized access to local instances. The flaw was disclosed on October 6, 2025, and has been assigned a Critical severity rating with a CVSS score of 9.7 (GitHub Advisory, NVD).

The vulnerability stems from insufficient host validation in the SillyTavern web interface, which makes it susceptible to DNS rebinding attacks. This technique allows attackers to bypass browser Cross-Origin Resource Sharing (CORS) restrictions by manipulating DNS resolution to treat malicious external sites as trusted local domains. The attack can be executed by tricking a victim's browser into resolving an attacker-controlled domain to 127.0.0.1, effectively granting unauthorized access to the local SillyTavern instance's backend API (Security Online).

The vulnerability enables attackers to gain full control over victim's SillyTavern instances without requiring direct exposure to the internet. Successful exploitation allows attackers to read private chat logs, install malicious extensions, inject arbitrary HTML for phishing attacks, and access stored API keys and configuration data. This affects all installations hosted on local networks or Termux mobile environments if users visit a malicious website while SillyTavern is running (GitHub Advisory).

The vulnerability has been patched in version 1.13.4 through the introduction of a server configuration setting that enables validation of hostnames in inbound HTTP requests. Users can enable this protection by setting hostWhitelist.enabled in the config.yaml file or using the SILLYTAVERNHOSTWHITELISTENABLED environment variable. While this setting is disabled by default for compatibility reasons, users are strongly encouraged to enable it, especially when hosting over local networks without SSL (SillyTavern Docs).