CVE-2026-44651 — sillytavern
CVE-2026-44651 is a Cross-site Scripting (XSS) vulnerability in sillytavern. A fix is available for sillytavern — see the affected versions and patch details below.
SillyTavern: Reflected XSS vulnerability in the CORS proxy middleware
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44651.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
sillytavernnpmDescription
Resolution
Fixed in SillyTavern 1.18.0: a user-provided URL is no longer reflected in the HTTP response body.
Overview
- Vulnerability Type: XSS
- Affected Location:
src/middleware/corsProxy.js:40 - Trigger Scenario: reflected XSS in CORS proxy error response
Root Cause
When fetch(url) throws, the code sends:
res.status(500).send('Error occurred while trying to proxy to: ' + url + ' ' + error).
The url value is attacker-controlled (req.params.url) and is not HTML-escaped before rendering.
Source-to-Sink Chain
- Source (user-controlled input)
- Entry point:
GET /proxy/:url(*)
- Data flow
- Code analysis shows concrete propagation into this sink:
- vulnerability title:
Reflected XSS in CORS proxy error response - sink location reached by attacker-controlled input:
src/middleware/corsProxy.js:40
- vulnerability title:
- The same sink behavior is confirmed by controlled execution observations.
- Sink (dangerous operation)
- Sink location:
src/middleware/corsProxy.js:40 - Vulnerable behavior: reflected XSS in CORS proxy error response
Exploitation Preconditions
- The attacker can inject controllable content into a rendered response.
- The vulnerable rendering context does not apply strict output encoding/sanitization.
- A victim user opens the affected page or response.
Risk
This issue enables script execution in the victim context and can compromise session or data integrity.
Impact
An attacker may run arbitrary JavaScript in the victim context, steal tokens, and manipulate user-visible behavior.
Remediation
- Never concatenate raw user input into HTML error responses.
- If URL echo is required, HTML-escape it or force plain-text output.
- Re-enable/strengthen CSP to reduce reflected injection impact.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | sillytavern | all versions | 1.18.0npm install sillytavern@1.18.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sillytavern, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update sillytavern to 1.18.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44651 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-44651 in your dependencies?
Find it across npm, including transitive dependencies.