Browser script execution via unescaped proxy URL
Published May 29, 2026 · Updated May 29, 2026
Reflected XSS in SillyTavern before 1.18.0 allows remote attackers to execute JavaScript in a victim's browser through a proxy URL. The CORS proxy error handler in src/middleware/corsProxy.js concatenates the attacker-controlled req.params.url value into an HTML response without escaping it. Exploitation requires a victim to open the crafted error response, after which the script runs in that victim's browser context and can read session data or alter displayed content.
Summary
What happened
Reflected XSS in SillyTavern before 1.18.0 allows remote attackers to execute JavaScript in a victim's browser through a proxy URL. The CORS proxy error handler in src/middleware/corsProxy.js concatenates the attacker-controlled req.params.url value into an HTML response without escaping it. Exploitation requires a victim to open the crafted error response, after which the script runs in that victim's browser context and can read session data or alter displayed content.
The record
- CVE
- CVE-2026-44651
- Published
- May 29, 2026
- Updated
- May 29, 2026
- Vendor
- SillyTavern
- Product
- SillyTavern
- Classifications
- CWE-79, T1189
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 29, 2026CVE publishedPublication date reported by the CVE source.
- May 29, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 1.18.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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