{"id":"CVE-2026-44651","aliases":["GHSA-xc4x-2452-5gc9"],"url":"https://o3.security/vulnerability/CVE-2026-44651","summary":"SillyTavern: Reflected XSS vulnerability in the CORS proxy middleware","details":"## Resolution\n\nFixed in SillyTavern 1.18.0: a user-provided URL is no longer reflected in the HTTP response body.\n\n## Overview\n- Vulnerability Type: XSS\n- Affected Location: `src/middleware/corsProxy.js:40`\n- Trigger Scenario: reflected XSS in CORS proxy error response\n\n## Root Cause\nWhen `fetch(url)` throws, the code sends:\n`res.status(500).send('Error occurred while trying to proxy to: ' + url + ' ' + error)`.\nThe `url` value is attacker-controlled (`req.params.url`) and is not HTML-escaped before rendering.\n\n## Source-to-Sink Chain\n1. Source (user-controlled input)\n- Entry point: `GET /proxy/:url(*)`\n\n2. Data flow\n- Code analysis shows concrete propagation into this sink:\n  - vulnerability title: `Reflected XSS in CORS proxy error response`\n  - sink location reached by attacker-controlled input: `src/middleware/corsProxy.js:40`\n- The same sink behavior is confirmed by controlled execution observations.\n\n3. Sink (dangerous operation)\n- Sink location: `src/middleware/corsProxy.js:40`\n- Vulnerable behavior: reflected XSS in CORS proxy error response\n\n## Exploitation Preconditions\n1. The attacker can inject controllable content into a rendered response.\n2. The vulnerable rendering context does not apply strict output encoding/sanitization.\n3. A victim user opens the affected page or response.\n\n## Risk\nThis issue enables script execution in the victim context and can compromise session or data integrity.\n\n## Impact\nAn attacker may run arbitrary JavaScript in the victim context, steal tokens, and manipulate user-visible behavior.\n\n## Remediation\n1. Never concatenate raw user input into HTML error responses.\n2. If URL echo is required, HTML-escape it or force plain-text output.\n3. Re-enable/strengthen CSP to reduce reflected injection impact.","published":"2026-05-29T17:49:19.494Z","modified":"2026-08-12T03:51:34.361060358Z","cvss":null,"epss":{"score":0.00323,"percentile":0.25423,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"sillytavern","fixedVersion":"1.18.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44651.json"},{"type":"ADVISORY","url":"https://github.com/SillyTavern/SillyTavern/security/advisories/GHSA-xc4x-2452-5gc9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44651"},{"type":"PACKAGE","url":"https://github.com/SillyTavern/SillyTavern"},{"type":"WEB","url":"https://github.com/SillyTavern/SillyTavern/releases/tag/1.18.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:34.361060358Z"}}